Here is a bizarre one for ya!

OK, here is one I have never come across before... I run a netgear firewall/printserver with a pppoe dsl connection at my office. Before I go on, this event has happened twice. I get to my office and my main rig is blue screened (all machines running XP Pro). I reset the machine, I get no IP address from the firewall (running as dhcp server). The main machine also takes a long time to boot, I open tasmanager as it is waiting to load everything, takes roughly 5 mins. I try to get to the firewall through the browser, try to ping it, nothing. I unplug it, reset it and reboot. Same deal, long boot time etc. When I do an ipconfig /renew, it says it can not contact the dhcp server.

Now, 1 machine (total of 3) can browse the internet no problem, get to the firewall. I look at the connected devices, it shows my main rig but NOT my 3rd. I think hmmm, that rig is down so i reset it. As SOON as i reset that machine, i go to the cmd prompt and type ipconfig /renew and bam! I get an ip, and all is good.

This brings me to the question. It seems this 3rd rig crashed and took my machine with it. It also prevented my machine from getting an IP and caused extremely slow boot times. Once restarted, everything was fine.

Could this machine be sending out some sort of massive ping attack? There is no virus on it, it is running ZAP and is a fresh install of XP Pro. The one machine that was unaffected had QoS Packet Scheduler installed, the other 2 machines I removed it, that is the only difference in the configurations.

If you have read this far, and have any ideas, any insight is appreciated!

What I would look at would be the Chipset drivers. Sometimes Windows thinks it knows what is best for your install and will install incorrect drivers. I have done this by accident several times at work for some of the PC's I manage at a college. The results were slow inoperable PCs.
You may have to check different NIC drivers. I had an issue with my cable modem one time where I could not sync and found out that Windows installed new drivers after a reboot.

Another thing to check would be to disable all other IDE chains through the Device Manager. Once there open up your Primary and Secondary IDE channels. Disable the ones that are not being used.
The reason I recommend this is it shaves off boot time. I have recommended this to a friend who had long bootup times and when this is disabled, it prevents Windows from looking for a new IDE device. Sometimes the scanning for new hardware is way too excessive.

on the netgear box you can set your log to record all network events. Try doing this to see what kind of packets that 3rd machine is sending out? Could you have that machine set up as a DHCP as well and there fighting?