Regarding Direct Memory Access

An unexpected error has occurred.
Boot selection failed because a required device is inaccessible.

A general group of people will initiate a fresh install upfront. However, it is to inform you that the problem is not as severe as it seems. To recover from the situation, it would require a Windows installation disc, as you are already incapable to boot into Windows. Listed below are the possible solutions for this issue, depending upon the reason of its occurrence.

• Rebuild Boot Configuration Data (BCD)
• Configure Active Partition
• Restore Master Boot Record (MBR)

Rebuild Boot Configuration Data (BCD)
The resolution is helpful, when your system is facing a spoiled Boot Configuration Data (BCD). In such a situation, it is recommended to rebuild this component of windows through command prompt. See below for a systematic procedure.

• Insert Windows Installation Disk and Restart your computer
• Select Time, Language, and click on the Next button
• Click on the words stating Repair your computer in the lower left corner
• Identify and access your system drive (For Example, C: D: E: etc.) and click Next
• In the System Recovery Options box, choose Command Prompt
• In the command prompt, type the command BOOTREC /REBUILDBCD and hit Enter

Configure Active Partition
The error 0xc0000225 may also result due to a wrong partition selected. The instance is that a user divides its storage device into several partitions. The BIOS must access the partition having system files on it (also called as System Drive). While accessing a wrong partition, it would end up in this issue.

• Insert Windows Installation Disk and Restart your computer
• Carry out the above given steps to reach System Recovery Options box
• Among several system recovery options, choose Command Prompt
• To set a correct partition, type the command line DISKPART and press Enter key
• In the listed partitions, determine the one to be active and type following command line
• SELECT PARTITION X (Let X be your desired active partition) and press Enter
• Once the partition is selected, type the command line ACTIVE and then press Enter
• Type QUIT and press enter to exit and then Restart the system

Restore Master Boot Record (MBR)
MBR is a boot sector containing information of logical partitions and file systems. An agitating MBR can also prevent you from normally booting into your Windows operating system. If this is the issue with your PC, try following steps to restore your MBR.

• Insert Windows Installation disk and Restart your computer
• Corry out the above given steps to reach System Recovery Options box
• Among several system recovery options, choose Command Prompt
• Enter the Diskpart and type the command line SELECT DISK 0 and press Enter
• Now type LIST VOLUME and press Enter key to view a new list
• Locate the CD/DVD-ROM under Type column and note down its letter under LTR column
• Close Diskpart by typing Exit and pressing Enter.
• Now access the CD Drive by typing F: and hitting Enter (Let F: be the CD/DVD-ROM letter)
• Type and enter CD BOOT and then DIR to view the directory within the drive
• Now type and enter BOOTSECT /NT60 SYS /MBR
• Type Exit and press Enter

At the completion of process, you will see a success message saying, Bootcode was successfully updated on all targeted volumes. Now you must not have any issue while booting into your Operating system.
Fix Boot Error 0xc0000225 in Windows 7

The obvious - Remove any USB devices like drives and any media from disc player. Its trying to load, but can't find bootable hard drive, CD, or USB...



Remove the hard drive and reseat (reconnect). Check BIOS. It must be listed! There is no going forward if it's not. Check boot order and make internal hard drive first. Save and restart.

One of your memory chips is bad.

Maybe your memory is bad or the memory slot is bad.

Remove the Power Cord, Open the Case and remove one of the memory chips. Set the chip aside then try rebooting the computer. If it boots, then you know the memory chip you set aside is bad so mark an x on it with an ink pen. If it fails to boot then move the chip to the next memory slot and try rebooting. If it fails take the chip out and set it aside, then put the other chip in and try booting it in both slots. If it boots, just to verify that the chip set aside is bad, mark an x on it and put it into the open memory chip slot and try booting.

Diagnostic Lights CAUTION: Before you begin any of the procedures in this section, follow the safety instructions located in the Product Information Guide. To help you troubleshoot a problem, your computer has four lights labeled "1," "2," "3," and "4"on the front or back panel. The lights can be off or green. When the computer starts normally, the patterns or codes on the lights change as the boot process completes. When the computer starts normally, the patterns or codes on the lights change as the boot process completes. If the POST portion of system boot completes successfully, all four lights display solid green. If the computer malfunctions during the POST process, the pattern displayed on the LEDs may help identify where in the process the computer halted.
NOTE: The orientation of the diagnostic lights may vary depending on the system type. The diagnostic lights can appear either vertical or horizontal.

Light Pattern

Problem Description

Suggested Resolution


The computer is in a normal "off" condition, or a possible pre-BIOS failure has occurred.
The diagnostic lights are not lit after the computer successfully boots to the operating system.
Plug the computer into a working electrical outlet and press the power button.


A possible BIOS failure has occurred; the computer is in the recovery mode.
Run the BIOS Recovery utility, wait for recovery completion, and then restart the computer.


A possible processor failure has occurred.
Reinstall the processor and restart the computer.


Memory modules are detected, but a memory failure has occurred.

• If you have one memory module installed, reinstall it and restart the computer. (see "Memory" for instructions on how to remove and install memory modules.)
• If you have two or more memory modules installed, remove the modules, reinstall one module, and then restart the computer. If the computer starts normally, reinstall an additional module. Continue until you have identified a faulty module or reinstalled all modules without error.
• If available, install properly working memory of the same type into your computer.
• If the problem persists, contact Dell.

A possible graphics card failure has occurred.

• If the computer has a graphics card, remove the card, reinstall it, and then restart the computer.
• If the problem still exists, install a graphics card that you know works and restart the computer.
• If the problem persists or the computer has integrated graphics, contact Dell.

A possible floppy or hard drive failure has occurred.
Reseat all power and data cables and restart the computer.


A possible USB failure has occurred.
Reinstall all USB devices, check cable connections, and then restart the computer.


No memory modules are detected.

• If you have one memory module installed, reinstall it and restart the computer. (see "Memory" for instructions on how to remove and install memory modules.)
• If you have two or more memory modules installed, remove the modules, reinstall one module, and then restart the computer. If the computer starts normally, reinstall an additional module. Continue until you have identified a faulty module or reinstalled all modules without error.
• If available, install properly working memory of the same type into your computer.
• If the problem persists, contact Dell.

Memory modules are detected, but a memory configuration or compatibility error exists.

• Ensure that no special memory module/memory connector placement requirements exist.
• Verify that the memory modules that you are installing are compatible with your computer.
• If the problem persists, contact Dell.

An other failure has occurred.
This pattern also displays during System Setup and may not indicate a problem.

• Ensure that the cables are properly connected to the system board from the hard drive, CD drive, and DVD drive.
• Check the computer message that appears on your monitor screen.
• If the problem persists, contact Dell.

After POST is complete, all four diagnostic lights turn green briefly before turning off to indicate normal operating condition.
None.

The swettings for DMA can be often found in the BIOS

getting into the bios itself varies by computer model but the common method is to press DEL (delete) repeatedly during switch on until it is shown.

Some computers may use other keys eg. F2 etc and quite often it may tell you on the bottom or top of the screen as you power on

the setting itself can often be found under the hard drive settings and may even refer to UDMA.

Some Bios have a single DMA / UDMA setting that you may have to look for in there.

This setting can greatly increase the hard drive and CD ROm access times for your benefit.

Press either delete or f2 during the boot up process to enter BIOS you can change or remove your password from there
good luck

Make sure you do not have a bootable CD or DVD in the drive. If that does not resolve, then try holding the "home" (Media Direct) button while pressing the Power button on.

When you hit the power button on your computer a whole lot of stuff happens. We call this the boot process. In the days when I first started using computers there was literally a "boot disk", a floppy (5.25" not a 3.5") disk that told the system where to go and what to do so that the operating system would start up. Since then the boot sequence has become somewhat more complicated. So let me take you thru the steps the computer takes to get started. For my example I'm going to use a Windows XP system.

1. First is the POST, this stands for Power On Self Test, for the computer. This process tests memory as well as a number of other subsystems. You can usually monitor this as it runs each test. After that is complete the system will run POST for any device that has a BIOS (Basic Input-Output System). An AGP has its own BIOS, as do some network cards and various other devices.
2. Once the POST is complete and the BIOS is sure that everything is working properly, the BIOS will then attempt to read the MBR (Master Boot Record). This is the first sector of the first hard drive (called the Master or HD0). When the MBR takes over it means that Windows is now in control.
3. The MBR looks at the BOOT SECTOR (the first sector of the active partition). That is where NTLDR is located, NTLDR is the BOOT LOADER for Windows XP. NTLDR will allow memory addressing, initiate the file system, read the boot.ini and load the boot menu. NTLDR has to be in the root of the active partition as do NTDETECT.COM, BOOT.INI, BOOTSECT.DOS (for multi-OS booting) and NTBOOTDD.SYS (if you have SCSI adapters)
4. Once XP is selected from the Boot Menu, NTLDR will run NTDETECT.COM, BOOT.INI and BOOTSECT.DOS to get the proper OS selected and loaded. The system starts in 16-bit real mode and then moves into 32-bit protected mode.
5. NTLDR will then load NTOSKRNL.EXE and HAL.DLL. Effectively, these two files are windows XP. They must be located in %SystemRoot%System32.
6. NTLDR reads the registry, chooses a hardware profile and authorizes device drivers, in that exact order.
7. At this point NTOSKRNL.EXE takes over. It starts WINLOGON.EXE that in turn starts LSASS.EXE, this is the program that display the Logon screen so that you can logon.

DMA is Direct Memory Access : http://en.wikipedia.org/wiki/Direct_memory_access

It should be automatically enabled, but if it is not there will be no damage. DMA simply speeds up access.