PDC – NT 4.0

I have a PDC and last time, it was sitting on a file server. Then the server crashed and I have no other server available so I promoted our Proxy server 2.0 ( which was a BDC) to become a PDC. Then it starts giving problem…
the Proxy server givesintermittent problem..it will stop all the Internet service and disallowing the user to browse the Internet. It happens once or twice a week. and I have to restart the proxy server to resolve it..It is not due to the Proxy cache becoming full.
Before promoting the Proxy server to a PDC, it never stops its services intermittently like what I am experriencing right now…
Can anyone advice me whether PDC is best to be installed on a server where it doesn’t share any applications?