PC running Windows XP shuts down unexpectedly few minutes after I log-in

[MisterK]

My PC running Windows XP shuts down unexpectedly few minutes after I log-in as Adm but not if I log as Guest.

If I am logged as Guest all is normal (so I guess it is not a hardware problem). When logged under Administrator, even if I don't run any program, the shut down happens 5-10 minutes later. I've had this problem with my desktop for the last 2 weeks, never before (this may be related to the recent installation of the BT Yahoo wireless Hub and all the programs that are installed automatically and that run on start-up, maybe conflicting with other processes.)

How can I zoom in on the fault ? can this be a virus ? any utility I can use that could shed some light on what is happening there ?

I have an eMachine L4S5MG, 2.0GHz Pentium, 512MB RAM, 80GB HDD, with a NetGear Wireless USB adapter.

Thanks for all your help !

[AWS]

There must be something running as admin that is causing this.

 

Right click my computer.

Select advanced tab at top.

In system starup and recovery make sure automatically restart is unchecked.

 

Next time the computer reboots a blue screen will appear with an error code. Post the error and I can troubleshoot it better.