You will not see a prompt on the screen for F8.  It is a matter of timing:  when you see F2/F12, start tapping F8 once or twice per second.  If you see the Windows logo appear, it didn't work and it's too late.  If you can get there, choose LKG; if that doesn't work, you can try System Restore; if that doesn't work, then I would boot to a Windows 7 DVD, choose Repair Your Computer, and let it do a Startup Repair; if that doesn't work, then choose Command Prompt and type in "chkdsk /r" (can take up to an hour or more).
All, Hope I can get some advice on how to proceed with this issue.Some Background:          I have had my Dell XPS 8100 for a year or so and it has worked beautifully. The original virus protection was set to expire, so I decided to install a new version off a store-bought disc. The software initialized, ran some initial checks, downloaded updates, and then removed the old software. Once it did that it poped up a screen asking to reboot to finialize the install.Only when the reboot took place, I got a black screen after the windows logo finished. This is before what would be the signon screen. And the windows version is 7. Since I had to do a hard shut down, when it boots up again, I get a screen that tells me it was improperly shut down and I can now choose to go into safe mode, safe with networking, or safe with cmd prompt.. or start windows normally. These are the only options.. I do not see anything about using last good configuation. No matter which option I choose.... safe or normal... I get the black screen with a mouse pointer that I can move. But nothing else. What steps should I take next to try to resolve the issue? Thank you!!
XPS 8100 Black Screen after initial Windows 7 logo