The font is fuzzy..... heres what happens as she said to me

shes running win xp and I told her to adjust her font setting but she said she can see the proporties, than general and nothing else?

1. when i first boot up it not there it starts within about 30 mins
2. it appears to be very random
3. it first started when i got the computer (and it is brand new) and my friend came and sorted it by installing avg, ad adwawre and a firewall it stopped doing it for about 2 weeks then done it again so i done all the cleaning files on it and it was fine every now and again it does it but everytime i clean it is fine but this time it wont sort its self out it has been doing it for about a week now and ive cleaned it everyday it works ok for 2/3 hours then starts again.
nothing other than that has changed
4. yes the text in all applications are affected ( even games)
5. yes my anti-virus is up to date
6. yes if i reboot it goes away but for only 30 mins