|Long shot that sometimes fixes oddities:|
Go to "Device Manager > Your Network Adapter", right click it and select Uninstall.
If by any chance it asks if you want to remove Software then DON'T LET IT (probably doesn't say that in XP). Ignore other warnings. Restart computer.
This procedures has simply unhooked the driver, so it will then see your adapter as new hardware and setup the software again. It might happen to get it right this time.
Always pop back and let us know the outcome - thanks