V-ism ... well if only MMORPGs that crashes your machine, then I would say the problem is most likely that IRQ sharing ... just for your information those games really generate a lot of network activities
So if you have another onboard NIC try that one then ... the other option, in the BIOS there is usually an option to force the system to reallocate IRQ's ... unfortunately, I just can't remember what it was called though ... something like force DPMI update or something, but it's usually located in the PnP setting in the BIOS ... might want to give that a try ... the drawback is that this could actually cause your NIC or video card sharing IRQ with some other part of your system ... though in most cases this will only change the IRQ that is used (ie. not resolve the IRQ sharing problem)
Another option you might want to try is updating the driver for both the NIC and video card ...
In worst case scenario, you can always just bite the bullet and get a PCI NIC