I had a failed Vista installation. During the installation the screen went black, I turned off and on the monitor and got no input. I took a shower, went on with my life, and went back. The monitor still had no input. I turned off the computer and turned it back on.
Now no matter what, no matter what it is trying to boot from, bootmgr rules all. It can't find it, therefore, cannot boot from ANYTHING.
What do you mean it can't boot from anything? Do you mean you can't boot from your hard drive? You can't boot from the Vista install disk? Need a little more detail.
Did the hard drive make any noise? After you turned it of, then on, did is POST? Error code?
Have you tried pulling out the plug in the back of the PSU and holding the on button for 15 sec, then plugging the power cord back in and trying to boot? It sounds silly, but I do it all the time and it works like a charm.