Yeah? Well that can be her choice then. I'll suggest it to her. Although I'm not really inclined to if I'm the one who's doing all of the work. Unless I get compensation.
Windows 7 ran much faster than XP did on my parents' PC. Sempron 3000+ (1.8GHz I think? Single core anyway) with 1GB DDR2 RAM and a 40GB IDE HDD...
Probably could have sped it up quite a bit switching it to a SATA HDD.