BOAC My experience with RJ45 into a USB might help (might not)
I used the adapter without any probs on two computers without network cards. (at different times) Then when I introduced WiFi into the house the computer using the adapter worked erratically and then froze.
The locked up computer recovered when the adapter was disconnected and a reboot was performed.
My solution was to dump the adapter in the bin and go wireless on that computer.
Can you put a network card in the PC?
Sorry I cannot explain why this happened - but I'm feeling better now.
MC