i have tried quite a few prgrams in the last years but reacently i have found a program called avira antivir it is a very good program you can get a free one just like AVG or you can download the full program from their website for about 12£ which is a very good value i reccomend it for eveyrone as far as i can see it is not very widely known but before purchasing it i made some research and it seems that many large companies use it for their employees it does not slow your pc much and it give excellent protection you can get the free copy from here
http://www.free-av.com/