Losing internet connection after 5 mins?

My laptop keeps dropping internet connection 5 mins after switching it on. My home network consists of 1 desktop and 2 laptops (Desktop and 1 laptop running XP and 1 laptop on Vista). The desktop and vista laptop get internet connection just fine but the laptop running XP is dropping its connection 5 mins after switching it on. I am connecting via a Netgear rangemax router. It stays connected to the router as I am able to see the shared folders on the other computers. I use Firefox and IE and until yeterday evening they both worked. As far as I am aware nothing has changed on my system. I have tried running spybot, ad-aware, AVG virus scanner, Clamwin anti virus, windows defender, CCleaner (inc registry scan) and Norton virus scan (which is in part of the Lenovo recovery console). I updated them all before using them. I have tried system restore (which refused to work). I have run hijackthis to see if I can see anything that should not be running as well as gone through the startup items and services in msconfig. I am able to ping google with no packet loss. I dont have all those cleanup programs installed, I run them from a flash drive so it is not a conflict of antivirus programs either. It is also worth nothing that messenger programs like skype and MSN stay connected and usable it just cant display a web page. It cant be an IP conflict as the router uses DHCP to assign the address's. It has worked perfectly for the last 2 years and has never caused a conflict. Also, it would assign a new IP on reconnection if that was required and believe me I have re-started lots of times trying to solve this. I have tried renewing the IP during connection testing through windows. Short of re-installing windows I cant think what else I can do which would be a shame as apart from the internet problem the laptop runs great.

Any ideas anyone?

Alexgtbeetle