System keeps rebooting at random

for the past few days my windows 7 Pro system has been freezing and rebooting at random.

I use an unRAID NAS and because i has having a problem with windows leaving NAS files open they reccommended that i make the following registry changes:

Set HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management\LargeSystemCache to 1
Set HKLM\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters\Size to 3

http://alan.lamielle.net/2009/09/03/windows-7-nonpaged-...

i don't know if this is what is causing the rebooting issue or not. I exported a backup of the registry before i made the changes. once i discovered the problems i tried ti import the registry backup file to restore the original settings and it started to process and then gave me an error saying that it couldn't import the .reg file.

so i went in and manually changed the values back but my PC is still rebooting.

like I said - this may not have anything to to with the rebooting - could be a coincidence but i would appreciate any suggestions on how to troubleshoot this,