Ooooh er! I've never had any problem with Bootvis, but Googling around, it seems that other people have.
This seems to be caused by running the bootvis program with tracing enabled
Try hammering on F8 as the PC starts up (don't allow it to fail and then give you the choices) then choose Safe Mode
Look at
http://mike-devlin.com/windows/ - there are some suggested solutions there.