Well normally i wouldn't have a problem with something like this, previously i've just logged into the router, gone onto wireless settings. And allowed a new wireless device. But the default login for the router isn't working, no one has changed it, and it came with no manual with a login/password in.
I'm using the Belkin wireless utility instead of the Windows default wireless utility, and i can see the network and connect to it, but it just seems to refresh and do nothing. Solved this on my laptop by installing the disk, but the PC comes up with the WPA error as i said.
I'll try what you suggested in the morning, hopefully it works, cheers