Windows Vista Removing Windows Vista

I have been working with a novice computer person who decided, without any investigation, to download and install Windows Vista over her Windows XP. Not knowing that the Vista and IE7 had ActiveX issues she determined it wasn't for her but asked for help to remove the Vista so she can go back to XP. However when she tries to boot from the Windows XP Disk she gets the message cannot install XP due to an incompatibility issue. Any suggestions?

 

If she has done an upgrade install of Vista over her current XP then Microsoft say that you cannot revert back to XP. The only option is starting again with a new install of Windows. http://www.windowsreinstall.com/winxphome/sp2installxpcdoldhdd/indexfullpage.htm

 

That's what I thought.

Thanks