No, not the same disk... one is a Dell upgrade, one retail, 1 x64 upgrade, and 11 32bit upgrade.
Something they have in common is Adobe Master Collection CS3, so I thought that might be the cause, so I reinstalled without it and sure enough explorer.exe shut down on me. I use Microsoft Security Essentials on all of them, so I guess that could be it too.. I will get you some dumps when I get back to work!