Internet explorer problems

Ok first i'll give you a rundown of my problem then list everything that i've tried to fix it. I'm running a hp pavillion computer with windows xp. About 3 or 4 weeks ago i caught a virus couldn't fix it so i reformatted my drive not once but twice messed something else up lol. Then everything was running fine no problems faster computer everything good then this past week all of a sudden boom, my internet stopped loading some websites. At first i thought it was just the site because it was a school site then i went on my laptop same network and it worked fine. So now like every 1 in 3 sites doesn't work. I can get my homepage and google and that's pretty much it. I've searched and searched for a soultion and still nothing here's what i've done.

1. Updated to ie 8
2. downgraded to ie 6
3. upgraded to ie 7
4. registered the 5 main dlls they tell you to
5. ran cccleaner
6. deleted all temp files and cookies
7. flushed ip dns
8. checked if it's automatically detected
9. ran norton 360 antivirus
10. turned off all antivirus software
11. reset modem, and router

I think that about covers it, please someone save me.