Sony Laptop Shut down problem

Have a Sony Laptop, P4 2.6 running Win XP Home w/512 Ram. Laptop will start running slow then just comp0letely shut down. Try to run Norton AV and half way thru scan it will just shut down. Same when trying to run Adaware. There seems to be about 62 processes running. Can not keep this running to do full scans to find out the problem. When trying to go into safe mode it stops responding after the screen showing the drives strating up,

Any suggestions on what I can look at?

The machine is used for autocad working with file sizes of 3500k.

Thanks,

Joe

If you're running on batteries make sure they are fully charged and/or use an external power source.

check your event log to see if there are any messages as to why it is shutting down.

With a P4 it may be that it is overheating. I seem to remember that they slow down when they start to over heat and then the system should turn off to protect itself from burning up.