Possible solution
I seem to have a fix here. I researched the Bad Pool Caller BSOD and it's usually triggered by a driver problem. Several Windows drivers were updated after installing ParallelsTools, so there was a good chance that this was the root cause. The one possible explanation is that Parallels causes Win7 to update drivers that in turn conflict with Parallels. This seems to happen when Windows attempt to update the drivers (mostly generic) that Parallels initially installs. I can't tell what the actual root cause is. But some of the before/after devices were markedly different. In my case, it appears that the BSOD came from the Intel SATA controler and the associated iastore.sys driver.
Also, this is really frustrating considering that I was a happy user of Parallels 6. All my troubles started after installing v.7 x86 
Anyway, here's the workaround that seems to work (about 20 clean shutdowns so far):
1. Open the Reliability History and find the list of drivers that were updated after installing v.7
2. In the Device Installation Settings, select "No, let me choose what to do" AND "Never install driver software from Windows update
3. In the Device Manager, uninstall each one of the drivers identified in the Reliability History and check the delete driver option whenever available
4. Reboot several times until Windows stops adding new hardware
If you hit a snag, you may want to follow the foregoing steps while offline.
Hope this helps. I'll post back if I run into another issue. I'm also hoping that the Parallels team can fix this going forward.
Last edited: Sep 23, 2011