By the sounds of it you don't know too much about computers (No offence ment). Windows XP is a operating system. it's what runs all your other programs. Did you mean to try and reinstall windows(or install windows for the first time) or did you just think it was some kind of program?
i'm sorry if you do know what windows is but just the way you it soounded, " this thing called WindowsXP ".
If you did mean to then is your HDD(hard drive) a SATA(Small red connector) or PATA(IDE)(Long connector usally grey)?
CPU-Intel Pentium 4 630 3.0Ghz / 2MB Cache ~~OS Windows XP SP2
MOBO-Gigabyte 8I915P Duo Pro Intel Socket 775 (PCI-E)~~HDD-Western Digital 160GB(SATA)
PSU-Aspire 500W ATX~~RAM-1GB PC3200 DDR SDRAM (512x2 Dual Channel)
GPU-MSI GeForce 6600 GT(PCI Express)~~Monitor Viewsonic VA902B 19" 8ms~~ ATI TV Wonder Pro (TV Tuner)
~~Still to come~~: eVGA e-GeForce 7800 GT