Please help: spontaneous reboot and freezing problem

I have a computer system at work that is having a lot of problems and any help would be appreciated.

Here are more details…

The system consists of four networked PCs running XP Professional. They used to be networked on my company network and part of a domain (with internet access). Then we took them off the company network and put them onto a seperate switch (with no internet access) and created a workgroup. The main software we are running is supplied by my company but let’s assume for the time being that the issue is not with that. The main problem is that all 4 of the computers intermittantly freeze up and will not allow a reboot (with the exception of hitting the power button). Also, sometimes the machines reboot on their own.

Does anyone have any ideas? Thanks.

Virus? Many virusses cause this issue. Despite the lack of internet access, can any of them be infected?

Also, do you have a particular computer set up to be the Computer Browser?
Right click “My computer”->Manage->Services->Computer Browser.

Only the server should have the “Computer Browser” service running.

what are you doing when this happens? have you checked the event log?