Thanks for the info - much appreciated.
I think it's coming round to the infection being still there, and in proquota.exe.
I did rename that file (while it wasn't running) to something else, and proquota.exe reappeared on the next boot-up. I've seen Windows do that before with other stuff, so wasn't unduly surprised.
I installed Avast, did a full update of that, and then left it doing a full check when I left her house last night. She's not e-mailed back to say what (if anything) was in the results of that, but she was embarrassed at having clicked on the virus e-mail, and that the children (aged between 19 and 30!) had turned off the protection on the machine.
I'll send her an e-mail to order Win 7 HP while I'm away, and I'll install it when I get back.
Understood on FAT32 for download/uploads. My portable USB 60GB drive is FAT32 anyway: it has to be, because I often use Knoppix to recover stuff from trashed PCs, and Microsoft won't allow Knoppix (or any Linux) to write NTFS format.
There must be a paying career for folks who go round mending PCs! I do lots of it, and am usually sent home with a bottle of good red wine.