Hi TAZZ,
The default Windows settings are to reboot in the case of a fatal error. You can get a better idea by disabling this behavior and see what blue screen error message is occurring. Try right-clicking on My Computer and selecting Properties. Select Startup and Recovery from the Advanced tab. Uncheck the Automatically restart setting and click OK.
My first guess would be the network device driver since you are trying to use the network. What driver do you have? Look in Device Manager and get the driver details (version, date).
Hope this helps.