The best way to get XP is :
- Put Windows XP CD inside CD/DVD Rom.
- In BIOS set CD-Rom as Primary Slave, and Hard Disc as Secondary slave.
- When you get message " Press any key to boot from CD " press anything.
- Now wait and follow the messages.
I pretty sure you know how to install Windows XP. I think there is no way to change Vista into XP, or XP into Vista ( maybe with themes, like brico pack, vistamizer , ...).
The best way to do that, install System again. Chose your favorite, Vista or XP.
XP include 64 bit too.
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