My computer is acting up!?

i have a good computer and i have anti-virus software aand 1 day is said a file was infected and i clicked delete and it said i was in the windos folder so it asked if i still wana delete it i said delete and now eveyy once and awile it pulls up a blue screen with white wrighting and it says it has encountered an error by pressing the esc on it goes to normal but i still want to fix the problem i have the origional windos disk for xp is there A way i can repair it by putting the xp disk in it or somthing!! please i need step by step! thanks!