Some years ago, I gave my In-laws a new Compaq Presario V5000 (with Celeron chip and small memory). It had SP2 on it, which I updated on various trips to SP3, etc. They had a problem and went to someone Dad knew, who installed Vista Premium (pirated, I'm sure), blew away all my security software and essentially made it unusable. I got it going again, but only by taking off all the security software. How can I restore this to it's original configuration? I have an original operating system CD which came with it.

You should be able to put the in the original CD, boot/reboot and the system should prompt you to install XP. Note, this process will reformat your drive, removing any programs and data that you may have. This install restores it to "factory" settings. If you have any documents, copy them off the laptop first!

If you want to "downgrade" (attempting to just replace the operating system and retain programs and data) from Vista to XP, that's another matter. Most articles I have read, don't recommend attempting this. And, it may not be possible with the disks you have because they are likely at set of "system restore" disks.

Perhaps the following link will work for you:

http://h10025.www1.hp.com/ewfrf/wc/document?docname=c01092639&tmp_task=solveCategory&lc=en&dlc=en&cc=us&site=null&lang=en&product=499847&key=null

Look for the section called "Things to do if you upgraded from Windows XP to Vista and want to return to XP".

If you cannot find this doc try:
- go to http://www.hp.com/#Support
- click "See support and troubleshooting information"
- in the product selector enter "v5000 laptop"

From there you should be able to find your Compaq model and the documentation I have mentioned.