You can get this type of error at the startup for many different reasons. I was getting one , every once in a while, from the microsoft intellitype mouse and keyboard software. Even installing the software from the cd that came with the KB-mouse did not solve that problem.
Generally you should have a memory dump file every time you have a critical stop. Here's Microsoft's site on how to read these files. If you have any it may tell you where the problem is.http://support.microsoft.com/kb/315263
This could also be caused by 3rd party software on the startup. You can use msconfig in the run box to disable software to see if any are causing the problem.Installing the run command in the start Menu
Open the start menu.
Right click in the dark blue at the botom.
select the advanced tab
In the start menu items field scroll down and check run command