I don't know where to began really... so i will just give it to ya
straight.

I have a Dell D600 with windows running XP Pro. 512MB of Ram 1.4 GHz.

1. the systems keeps hanging/freezing quite often.
2. periodically I will get the BSOD with different error codes each
time.
3. The NIC keeps disappearing from network connections and from the
device manager intermittently.
4. As long as I don't have anything plugged into the Ethernet port, it
seems fine. I am able to use the wireless capabilities without issue.

Things I have tried:

1. ran diagnostics (Dells utility and memtest).(no errors)
2. replaced ram with known good. (didn't help)
3. replaced Network cables. (tried know good)(didn't help)
4. uninstall and reinstalled drivers.(didn't help)
5. uninstall and let windows detect hardware again.(didn't help)
6. reinstalled OS.(didn't help)

I'm guessing hardware, but i don't know.

-Skip