If you cannot get AVG free to work then try avast which is also free. It isnt my personal preference however it does work well.
Be sure to get spybot s&d and also spyware blaster to protect against spyware malware and adware rubbish.
Finally get CCleaner to keep your PC clean of any things such as tracking cookies and other junk websites make you download.
However AVG8.0 is totally free I had it installed however it caused me some issues so had to revert to 7.5 for now. If you want me to send you a copy of AVG 8 by email or MSN messenger hit the yellow envelope and drop me a message. I would be more than happy to send a copy.