XP continously rebooting

[Navion]

Hi:
XP boots to desktop then after a few seconds it reboots. I have traced this to the cable modem and the USB connection. When the modem is not connected to the USB port it works normally. As soon as I connect it will start to reboot over and over. Then each time I get the message of "serious error has occurred". I have re-formartted the HDD and re-installed windows but no relief. I have dis abled startup items,loaded default bios options and nothing changes. I got a new modem and the same thing happened. Does this sound like hardware problems in the board?
THanks

 

[wolluf]

'When the modem is not connected to the USB port it works normally' - sounds like you've found the problem...

 

[littlerumper]

Is there an error in the event log that's more specific? If it's an RPC error, I'd scan for viruses as that could be msblaster. Is there a file running in the background called DLLHOST.EXE or MSBLAST? Regardless of the reload, without a firewall or antivirus software, an unpatched 2K/XP system is a magnet to this virus. Just worth checking for.