Vista/Win7 No Boot – Not Even Safe Mode

It first presents the nice splash screen asking about language and keyboard layout, and then after clicking "Next" it asks you for your product key. It is at this point that you can access a truly excellent feature of setup, obviously intended to troubleshoot a failed installation, but also VERY handy to administer a system that is on the fritz. By pressing SHIFT-F10, Setup runs "cmd", and drops you to a command prompt that is running with SYSTEM privileges.

RTM of Vista keeps the useful trick of hitting SHIFT-F10 during Setup
Summary: At the product key screen do SHIFT-F10

Additional:
Bootlog:
Press F8 key during bootup, select "Enable boot logging"
"Creates a file, ntbtlog.txt, that lists all the drivers that are installed
during startup and that might be useful for advanced troubleshooting."

Recovery Discs:
If you do not have Vista or Win7 Install discs, you can get the "recovery" discs here.