ok, try this log in to homehub , 192.168.1.254 go find the lan settings, and change the range to something else,ie 192.168.5.x, reboot router, login again to whatever you set routers ip to. and change them back to default. reboot again. then you should be able to get an ip address again. i have had to do this a couple of times with homehubs.
Have you tried the PC connected direct to the hub, if it doesn't work then you will know that the network adapter is at fault and will need reinstalling.
manually assign ip address 192.168.1.210, subnet mask 255.255.255.0 gateway 192.168.1.254 1st dns 192.168.1.254 leave other dns blank
I found Vista alright toward the end if it's life once most of the bugs had been ironed out, also once it's tuned up and all the crap thats not needed is disabled it's quite usable.
NEW PC TIME...i joke but seriously would consider this as an option even excluding the networking issues, get a cheap-o pc that will run windows 7 solidly and try the network adapters again, or get hold of another PC to test the network adapters on!
I found Vista way better than XP in fact I've got Vista ultimate 64 on two of my rigs never had any problems with it.