You might aswell get one from PC World, if she just wants somthing simple
Or i spose you could order a simple one off the internet..
http://www.aria.co.uk/newAriaSystems.asp
cheap an cheer ful i guess
For the old one.. i suggest that you do the following
1) Stop programs from loading when windows loads up
2) Update windows, any other drivers an programs
3) Anti-virus software updated, Anti Spyware Programs (Scan etc..)
4) Diskfrag.. Failing that
5> Back up all info, reformat, install fresh copy of windows, then install Anti-virus & spyware, drivers, update windows