What does boot manager do?

I started up my PC and I always have to press F1 to continue past the bios
message "Your CPU fan speed is too low". My monitor was off still while I was
spamming F1. When my monitor turned on, boot manager was open. I just pressed
enter cause Vista was highlighted. Then it started doing a scan or something.
I turned my PSU off and on cause I didn't need to do any scan or whatever it
was doing. I restarted my PC when the scan (or what was it?) was at something
like 3140/102 235. Now when I try starting up Vista I get a quick blue screen
and it restarts. I tried using my Vista DVD to repair but when I click repair
and it started repairing, I got a bluescreen. I really don't wanna have to
reformat...any idea what boot manager was doing?

PS: Posted 7/9/2008 7:38:11 AM
message detail I'm pretty sure it wasn't doing a chkdisk. Usually when it
does that it asks me if I want to do it and with that scan thing that
happened all it had on the screen was names of some files or registries and
and number like 2341/104 561 while chkdisk usually has a bunch of other
stuff.