Windows XP Service Pack 2 is usually a good thing. However, it's not without it's problems. Most notably is it's crashing of more 'sloppily' written drivers. If you're now experiencing the BAD_POOL_HEADER Blue Screen Of Death on bootup and have a NetGear wireless network card in your machine, then remove it. More than likely this will allow you to boot. I've also heard of some LinkSys wireless network cards causing this same error as well. As of the writing of this article, there are no new drivers from either LinkSys or NetGear. I've also been unable to find any support on their site about the issue. If your NetGear card uses the Atheros chipset, then you may be able to use those drivers to get back up and running.
Note: If you still can't boot even with the card removed, or into safe mode, you'll need to use the recovery console to disable the driver.
The Indexing Service will, on occasion, also cause SP2 to crash. I suspect that machines that start to exhibit this symptom after having SP2 installed have greater underlying issues. Anyway, to stop the indexing service from running, then click Start->Run type services.msc, and click OK.
Indexing Service BAD_POOL_HEADER
Double click the Indexing Service and set the startup type to either manual, or disabled. By default, I believe it's manual. (You'll notice on this machine it's not running, and is set to manual. I haven't changed the setting at all. Also, this machine is running SP2) If your machine BSOD's upon bootup, then you'll likely have to boot to safe mode to change this. You can also disable the Indexing Service using msconfig, however, it's generally better practice to do it the services.msc way.
http://www.tweaksforgeeks.com/BAD_POOL_HEADER.html
