This may work for Vista SP1 also, but it may not. I just know that it solved my Windows XP SP3 issue.
On my Mac Pro at home, I have a 100gb partition set up for dual-booting Windows XP with Boot Camp. I also have Parallels set up to use this BC partition in a VM.
While in the native Boot Camp install of Parallels, I installed SP3 for Windows XP (after updating to Boot Camp 2.1, this is IMPORTANT as it updates the drivers on your machine). Fortunately, my machine survived just fine, so I moved back into OS X.
In OS X though, I wasn’t so lucky. The machine got into a reboot loop with the error message AUTOCHK NOT FOUND. Suck.
The solution is to open Parallels…
Select your Boot Camp VM
Edit –> Virtual Machine
Go to the hard disk listed in your VM.
Click “Clear” to clear the hard drive information on your BC install.
Start your VM.
Notice it boots fine. Yay!
REINSTALL PARALLELS TOOLS.
All should be well!
Hope this helps.