Have you checked for spywares and mal wares or viruses?
In case it works abit and stops another time but you are still connected, then i recommend fixing your win socks using
this
quote:
Originally posted by WinSockFix description
WinSockFix will offer a last resort if your Internet connection is corrupted due to removed or invalid registry entries.
It can often cure the problem of lost connections after the removal of Adware components or improper uninstall of firewall applications or other tools that modify the XP network and Winsock settings.
If you encounter connection problems after removing network related software, Adware or after registry clean-up; and all other ways fail, then give WinSock XP Fix a try.
It can create a registry backup of your current settings, so it is fairly safe to use.
Note: Be sure to read the "Info" before running this software.
Also make sure there is no firewall preventing you from using the internet.