"She now has her WinXP borked by antivirus 2010, and claims it came from linux."
it is not possible with the virus called antivirus 2010
this specific virus comes in the form of a trojan, it can be inside of messenger shared files, also a mail
it can come inside a screensaver, those you download and get tons of publicity booting with the desktop
the file modifies registry and changes names of files inside c:windows/win32 and other places, if you search for my post talking about it, you will find information about it
if she found a page infected with a variant of it, it would require to run wine and add the registry entries on the windows partitions and that in this moment sounds very hard to do
this particular virus/spyware/trojan/scam is hard to remove and once you remove it, it usually destroys the antivirus that should stop it in the first place
doing short the history, install a good antivirus like avira, avg or avast free versions, force her to use only opera or firefox, help her learn to use anything but live menssenger(trillian or pidgim) but before all that do a good backup of that xp partition and format that partition because you will need to reinstall win xp, this crapware damages the installation and disables the antivirus, the task manager and other system menus that are required
windows is great isn't?