Test your PSU power supply unit or replace it if your power supply units fan is not working your PSU is faulty
http://pcsupport.about.com/od/toolsofthetrade/f/powersupplytest.htm
One bad lead can cause a computer to continue on a cycle of restarting or to shutdown or fail to detect/ boot up a computer hard drive
Test all leads that attach to your hard drive power and data cables IDE SATA
the leads from your MOTHERBOARD TO YOUR HARD DRIVE make sure they have a secure dust free connections and are not faulty or just replace them they could be faulty make sure all leads that are attached to your dvd\cd floppy drives have secure connections and are not faulty or just replace them they could be faulty computers need power and data to travel through every working device to continue its cycle and have an end so any faulty leads will end up with a computer error even something as small as a faulty electrical or fan lead can cause you problems
motherboard and a hard drive any leads between them will fail before your motherboard or your hard drive if its a flat ribbon 40 pin type IDE replace it this will be the first to fail
check all electrical power input and extensions make sure they are securely seated even the cd/dvd floppy drives need to have current go through make sure these drives are working
also check the Cmos battery and computer RAM modules make sure they are securely seated with no dust built up or in the sockets on some motherboards cmos batteries are soldered inif this fails to fix or isolate the problemRestart your computer repeatedly tapping the f8 key to enter safe mode while the screen is black once in safe mode where the only things working will be your keyboard and mouse allowing you to attempt to repair your computer.
You could select the option start at last known configuration that worked this will tell you if and what file has been corrupted or missing then you will know if its a hardware issue and work your way through the problem. if the problem still persists f8 back into safe mode you might need to select your operating system to load into safe mode. You might use the system restore to restore your system to an earlier time click start all programs accessories system tools you should see your system restore option if it is a hardware issue the system restore might not work Manual restore points that you specify with the System. Configuration utility Installation restore points that occur before you install a program or a service you can use the system checkpoints or the installation restore points to restore your computer's settings to a date when it operated correctly. This may also help determine the cause of the configuration error.To perform a system restore, follow these steps:1.Click Start, click Run, type msconfig, and then click OK.
2.On the General tab, click Launch System Restore.
3.Select Restore my computer to an earlier time, and then click Next.
4.Calendar dates in bold are possible restore points. Click the most recent one to view system restore information.
5.Select a system checkpoint or an installation restore point, and then click Next.
6.Close all other programs.
7.To start the system restore, click Next.
8.Your computer restarts.
Repeat steps 1 through 8 until you fix your configuration issue.
if you need more help with this post a reply with either deskop or laptop hope this helps
The latest versions of Windows, including Vista and 7, use the Windows Boot Manager to read the boot configuration files and data in order to load your Windows Desktop.
If any of these files are corrupted or damaged, you will see a "BOOTMGR is missing" error. Fortunately, you can use a number of Windows tools to repair or replace the BOOTMGR or any related file that may be the cause of the problem.
Insert your Windows installation CD disk in your computer's CD drive and restart the computer.
Press "F8" repeatedly while the computer boots up.
This command enters the "Advance boot options" screen.
Select the "Repair my computer" option and then press "Enter."
The System Recovery Options screen opens.
Select the "Startup Repair" option at the top of the list and click "Next."
The utility will scan your system for the cause of the BOOTMGR problem and repair it.
Hope this helps
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