A quick Google search shows a few people with this same issue in Windows 7. The fix seems to be restoring backup copies of corrupted registry files.
Excerpted from a conversation on social.technet.microsoft.com:
"I first booted from the Windows 7 install disc to get to the system recovery console. I then selected Command Line. From there, I had to change from the X: drive to the C: drive by typing "C:". I then typed "cd\ windows\system32\config" to get to the registry file directory. By typing "dir" I could see that two of the five hive files (default, sam, security, software, and system) had recent copies with an "rmbak" extension: default.rmbak and software.rmbak. I then executed the following commands:
ren software software.bak
copy software.rmbak software
ren default default.bak
copy default.rmbak default
I would suggest you execute the "ren" then "copy" commands as above for any other hives that have "rmbak" backups with the same date/time stamp. This ensures your registry remains in sync. You can now reboot and see if your computer comes up.
Some variation on that fix might be just what you're looking for.