I need help with a window xp computer virus help or something else?

Imy friend has an old acer computer with windows xp and it was worked on by his brother he tried to put Vista on it or maybe windows seven. Anyways there is literally no programs on the computer anymore like internet explorer Microsoft office and any program that came preloaded on the computer is gone like the accessories folder anything under start tab and under all programs is gone and empty it won't connect to the internet and it will just randomly shut down any advice. I was thinking of maybe going back to a certain point on the computer but I can't access the folder to do so everything is gone but controll panel and some other folders I can access wireless settings but nothin really else but Windows recovery keeps coming up trying to fix the hardrive and wants me to pay for the program but then I can get online.e any help besides taking to a specialists?