Thankyou for your responses. After I posted this thread I did a bit of searching online (should have done so before posting really). I am aware that there would have been compatability issues with drivers and the like and would require a fresh install of OS which I'm not prepared to do. I came to the conclusion that the systems are in dire need of more RAM. I have ordered 2Gb for each machine with the option of purchasing more if need be. I'll asses the situation in the near future and will more than likely upgrade the whole system with new PC's and server.
Thankyou once again.