web site viewing help

man i don't get this. I can't go to certain sites on this computer. like support.microsoft.com. or lolli.org, or bearshare.com I don't get what the fuck is up with this, I have no firewall up, my security settings are at medium level as default, yet I go on another comp it works fine. Everything is default. Can someone help? please e-mail me digitillusionz@yahoo.com thanx