i guess you gotta put into consideration that windows computers are targeted by much much more viruses than macs.

did you update constantly and have good knowledge of windows xp?

and the problem may have been a hardware one.. not a software one..
like some say dont get compaq.. while others say dont get hp.. and others say dont get dell.. acer etc.. personally dell has never failed me..

but i as well had a compaq computer become an expensive paperweight.. for no apparent reason