safe mode locked out

Safe mode is locked out, attempted to install Avast5 just after paying for a 3 user sub and now my PC is frozen.
The safe mode screen is displayed but no mater what choice I pick it goes into a cycle mode none of which allow for input, cant get back to a recovery point either. running XP.

any sugs?? out there.

Which is your old antivirus before avast? How did you uninstall it?