I want to install another xp copy that I downloaded and burned in a CD.. the question is.. If I choose setup windows will it delete all files in all partitions? or only C partition the partition i'm installing windows on?
Depends how you have it install, if you install Fresh XP over Old XP then you would be told it will install a Fresh Copy on C, and move the current XP to Windows.OLD directory and such. If you evoke a Full Clean install, it doesn't wipe the drive, it just installs over the directories but leaves many broken programs, directories and files, littered all over the drive to cause mayhem down the road.
Now if the current Windows on there is VISTA or 7 - XP WILL NOT INSTALL. It will tell you the computer is already upgraded and you have to still do my suggestion below.
The best option would be to use a Diskwipe tool to clear the partition (NOT THE DRIVE - BE CAREFUL), then do a clean install (ALWAYS RECOMMENDED) on the C partition. This is highly technical and I wouldn't try giving you a step by step.
The best solution would be to use a external drive connected to your computer, and a simple OS on DVD like UBUNTU, that loads up in memory, then move the files you want to keep (you can't keep the programs, the parts to them are scattered everywhere and you can never get all the files) to the external drive then do a complete DRIVE WIPE, and do it clean.
NOTE: XP is NOT SUPPORTED IN ANYWAY. XP update files are not included on websites anymore, nor are drivers. It is best to go with Windows 7 at a minimum.