My computer connects to the internet from a shared network with my room mate. Every so often my internet connection just dies and his doesnt. Even after rebooting the computer the internet connection will not be established. I replaced the harddrive on the computer and reinstalled then the internet started working again. This is the 3rd time ive gone through this cycle. Does anyone have any idea what is going on with my computer?

Well, obviously it's not a hw issue, because you wouldn't be able to connect in the first place. (Actually, it could be hw, like if there was a short somewhere, but it's highly unlikely).

Are you running wireless or wired? If you plug the modem directly into your system, does it still die? Does your computer go to sleep, which may lead to it losing the connection? Have you updated all your relevant drivers?

your connection does work spiratically do you have a firewall program that can be blocking your connection have you ran a spyware scan to check for malicious applications running in the back ground when did it start doing it have you installed any new programs on the computer. If you are using XP start in safe mode with networking by pressing F8 when you are booting the system do you get a connection in safe mode it sounds like a definate software issue I vote firewall or spyware