Compaq computer freezes or hangs

this link should help you out.
Compaq Presario Desktop to Factory Google Search

First things First!

Usually, restoring your PC, involve, a series of DISK, or CDs, or even restore from your hard drive restore partition,
check your BIOS for restore, or what combination KEY, from the keyboard,is designated for restoring, usually its, F11 or f10
good luck
Carl

It would be better if you share the OS installed on your PC. If you have any version of Windows then there is an inbuilt setting for restoring system. You just need to search it. If you have a Mac OS then use the "Restore from the Time Machine" utility provided by Apple. Or you can use any third party software like Faronics Deep Freeze to restore your computer.

If your Computer hangs or Freezes up, it means:

You have too Little Ram. You need to Increase Your Ram to 3 or 4 GB. You Ram Controls How Fast Your Computer Processes Applications Including Game Software.

If After Updating Your Ram to More than 3 GB, You Continue to Experience the Freeze, You can Perform a System Restore (System Recovery for XP) and Restore Your Computer to the Same Condition as if You Just Bought it. However, I would Highly Recommend that you Save all Pictures, Music, Documents, Videos, Games Etc. on a 500 GB Seagate External Hard Drive, and then perform the System Recovery. Otherwise all Your Files will be LOST!

Preforming a system recovery to return the computer to its original condition may be necessary if the operating system is damaged, or the hard drive is corrupted, or the computer is infected by a virus.

___Also look this> HP expanded the battery pack recall on May 19, 2010. Click here to validate your battery. Performing a system recovery removes all software and files saved to the hard drive, reinstalls the original operating system, and then configures the settings for the default programs. Since the merger of Compaq and HP, several different recovery tools and processes Names for these tools include: Recovery Solution, Recovery Manager, F11, Recovery Disc, Driver and Application Recovery Disc, Roxio BackOntrack, Microsoft Backup & Restore. have been provided for recovering notebook PCs to their original operating condition. To help you select the correct recovery process, the table below identifies the different models, the time frame when they were produced and sold, plus the originally configured operating systems. Click on the name of the document in the right column for detailed information. Choose the Correct Recovery Process for Your Notebook Notebook description Recovery procedure information HP and Compaq Notebook PCs and Mini PCs shipped with a Windows 7 operating system. Recover Windows 7 Operating System Using HP Recovery HP and Compaq PCs using the Microsoft recovery feature for Windows 7 instead of an HP solution. Recover Windows 7 Operating System Using Microsoft Windows Backup and Restore Presario, Pavilion, and HP Compaq Business PCs shipped with a Windows Vista operating system. Recover Windows Vista Operating System Using HP Recovery HP and Compaq PCs using the Microsoft recovery feature for Vista instead of an HP solution. Recover Windows Vista Operating System Using Microsoft Windows Backup and Restore HP and Compaq Mini with Windows XP using the HP solution. Recover Windows XP Operating System On Mini Notebook Using HP Recovery HP and Compaq Mini with Windows XP using the Roxio recovery feature instead of the HP solution. Recover Windows XP Operating System Using Roxio BackOn Track HP and Compaq Mini with Mobile Internet Environment (MIE ). Recover Windows MIE Operating System On Mini Notebook Using HP Recovery Presario, Pavilion, and HP Compaq Business PCs manufactured and sold in 2006 or later . Recover Windows XP Operating System Using HP Recovery (2006 or Later)

Presario and Pavilion PCs manufactured from 2001 and 2005 . Recover Windows XP Operating System Using XP Operating System Discs (2001 to 2005)

And

Recover Applications Using Drivers and Applications Recovery Disc (2001 to 2005) Pavilion PCs with Windows Media Center edition of XP manufactured from 2001 to 2005 . Recover Windows XP Media Center Edition Operating System on HP Pavilion PCs Using HP Recovery (2001 to 2005) Compaq Presario PCs supplied with a Compaq Recovery CD and manufactured from 2001 to 2005 . Recover Windows XP Operating System on Compaq Presario PCs Using HP Recovery (2001 to 2005) Omnibook and certain Pavilion PCs manufactured pre-2001 . Recover Windows XP Operating System and Applications on HP Omnibook and Pavilion models Using HP Recovery (Pre 2001)

Guardian, If you want to remove all SW that you installed and all the data that you have on the computer, then the easiest way is to go to Start->All Programs->Accessories->System Tools->Restore. Restore your PC/laptop to the earliest date that you can. The restorable date would be in bold numerals. Go backwards as far as you can and select the oldest bold date. The laptop would take a reboot after sometime. Do not panic. Just follow the instructions. Should you want the data for you, then back it up before restoring.Backup to a CD or a DVD.

Restore to factory settings? or a System Restore?

For factory restore (All Data wil be Lost), tab the f11 key while booting the computer and enter PC recovery. Go to Advance options and Select the option of "restoring the system back to factory settings". in case u do not go to PC recovery after multilple attempts, there is no partition. Use Recovery cds.

System Resore : All programs > Accessories > System Tools > System restore. Select a date and Follow instructions(No Data Loss)

if you have a windows cd you can do a system restore from it or at the boot screen some computers have a system recovery so you can use system restore without a disk, if you can use system restore, restore your computer to a earlier time and that should solve your problem

Your compaq should have come with a factory CD that will allow you to restore the system.

Insert the cd and restart the computer. It should boot from the cd and ask you if you would to repair the installation (or something similar).

Without the HP CD you can pretty much hang it up with a copy of Windows.

i would maybe look at any devices you have connected as the hanging may well be a corrupt driver or faulty hardware, but as always a process of illimination is required. i would suspect either a processor overheating or motherboard problem, as you have changed the ram and you mention that under load it happens frequently.