Help with debugging random rebooting problem

Hi There,

For some time now, my PC has been randomly rebooting itself every 15 minutes or so, though sometimes it remains on for many hours and then just reboots out of what appears to be nowhere (i.e. no obvious cause or predictability).

Running a full scan with security essentials seemed to slow this "reboot cycle" down.

I've also noticed that almost every time I attempt to apply a windows update or install new software it reboots and every time I try to access the 'backup and restore' management controls in the Control Panel on my PC it reboots without any warning...

I am able to select the software updates and download them (i.e. Windows Updates) and I can begin the installation of a new program (like Photoshop), but when it gets 99.99% to the end of the installation or update process my PC reboots out of nowhere before the installation or update can be complete or applied.

A friend suggested that it might be an incompatibly with the Motherboard and the RAM, but I've doubled checked that and they are compatible as far as I can tell.

I thought that this issue might be related to MS security essentials because it seemed to have some effect. So I successfully uninstalled it this morning and now I I've seen a blue screen (please see the attachment for details) every time it has randomly rebooted...

Is anyone familiar with this type of issue?
Does anyone have an idea of why this could be happening?

Your help is much appreciated!!