HELP cant figure out why i cant fileshare

SYSTEM:
Microsoft Windows XP
Proffessional
Version 2002
Service Pack 2

Hewlet-Packard
Pavilion
AMD Athalon(tm)XP 2800+
2.08 GHz, 512MB of RAM

Ok everyone this is the problem everytime I try to fileshare with programs like AIM it gives me a message saying i could possibly be under a firewall and to my knowledge they are all shut off...perplexing yes i know...Also when I try to upload info to sites such as myspace it tells me the service is unavailable...Ive already tried RUN: Firewall.cpl ... and still nuthing

If you have any info please reply this only started to happen like 2 months ago.

im almost ready to throw my computer out the window
-jeff