Seti@home not working, or other online programs

I've been having problems with this for a while. Some internet programs act like there is no connection to the Internet at all. IE 6 works, Outlook works, ICQ worked after changing the server, Download Accelerator works, WS-FTP works, GMud32 works and more work.

Unreal Tournament won't work online, or Half-Life, or Seti@home, MSN Messenger or Continuum. I use MSN as my ISP, and it won't let me sign in, but it connects fine (duh). I made such a big list because I'm hoping that will narrow down the problem. All of the programs that don't work say they can't connect to their server. Any help would be appreciated!

I fixed the problem myself, thanks for the reply and everyone who read the post I reinstalled XP, but what did it is finding the *ahem* correct format of signing on to MSN w/o using MSN Explorer. you have to type "MSN/username" for your username.