Chronic Slowdown of NT

I have an NT 4.0 machine, 512 MB RAM, 2 Processors with two drives in a RAID config….these people have the 2 drives sharing a RAID channel, so that accounts for some performance hits….but what have y’all learned to look for on a machine that has”chronic slowdown” problems and the admin says it just seems like a slow machine. He has done the basics well, unneeded services killed, static size paging volume twice the RAM, blah blah. Performance monitoring only reveals occasional high disk queue times I atrribute to the shared RAID channel.

Thanks for pointers!