virus?

yesterday my lap top detected a virus (worm) I have been out and bought a Norten internet security 2010 disc but says i dont have permission to run disc, I am on windows live and think maybe not right one as cover says wind vista wind 7 and windows xp is there anything i can do as getting worried ....pc keeps asking me to buy 80.00 cleaner on the error message it just says everything is at risk of infection please help