Vista - Black Screen and unable to finish Vista Beta 2 installation

I'm not able to finish up the installation as when the system boots up at the
very end of installation I'm getting a black screen. The first time I was
able to go into Safe Mode now I can't. I'm running a Dell computer with an
ATI Radeon video card.
At present I don't know what to do to get out of this issue.
I wish I could go to Boot.ini and change the option to log only on Windows
XP but I can't even go into a Safe Mode.
Does anybody have a suggestion on how to get arround this issue as my
computer is not operable at all. I'm sending you this message from my other
desktop which I'm glad I did not use to try Vista Beta 2.
Hope to hear from somebody soon.
Regards
Frank G.