Have you tried looking in the Event Viewer.
To access this ( right click My computer / left click Manage / left click Event Viewer / left click System ).
When you have the information, look for red circles that have a white X in them, (these are Errors) then look at source for your problem.
Right click one of the errors then left click Properties, this will bring up the Warning properties box, with limited information about the problem.
If you left click on the Microsoft link then left click yes it will go on the internet to give you more information about your Problem.