List of possible problems for Bad Pool Header...
* Drivers for some NetGear (and other brand) wireless adapters.
* Drivers for all kinds of hardware.
* Indexing service
* Conflict between active anti-virus scanning software and some CD burning software
Just a hunch...if you can get into Safemode and disable the Indexing service this may solve your problem.
This is something I do regardless because all it does is slow down your access times to your data on the HD's.
Select Start/Run ant type in: services.msc and hit Enter.
Scroll down till you find "Indexing Service". Right-click it, Stop it and set it to Disabled.
My other hunch is that your mobo is going bad.
This can cause all kinds of problems including file corruption even though test may show everything is OK.
At least that was the case with me one time.
Within 2 weeks it died completely after starting to have problems, but yours maybe working just enough to keep it going until now.
This would also explain all of your other problems you've had with your system before.
Here's a list of sites with Bad Pool Header and possible solutions.
WindowsSecrets.com | Everything Microsoft forgot to mention