Major Vista Boot Problem

Hi everyone,
I'm having some major problems with my system and thought I would see if anyone had some advice.
My system (running Vista Home Premium - see my specs), was working fine yesterday. It suddenly went quite sluggish, I shut all programs and reset. It had updates to install upon reset, so it went to an "Installing updates 1 of 6" screen. It sat there like that for about an hour and a half, until I finally gave up on it and powered down. When I started back up, I couldn't get it to boot, even to safe mode. Lots flashed onto the screen quickly, so I couldn't get it down, but it said "Registry file failure" and then would send me to the boot menu again.
I eventually went in and changed the order of drives it would boot off of, so I could boot from my Windows CD - did so, and ran repair. The only substantive message it gave while repairing was :
correcting error in index $I30 for file 2448

Since then, I have been able to get it to boot into safe mode (takes at least 20 minutes), but seem pretty limited from there until it crashes again. Upon startup (and some program launch), I often get the following error message:

"rundll32.exe Application error
The instruction as 0x7763f4a1 [note: sometimes different characters here] referenced memory at [same character string]. The required data was not placed into memory because of an I/O error status of 0xc0000185 [note: this character string is the same each time].
Click OK to terminate"

Also, when trying to run the device manager out of safe mode, I got the following error:

"mmc.exe - Bad Image
C:\Windows\system32\MFC42u.dll is either not designed to run on Windows or it contains an error...."

I've gotten that message with another .dll file as well but didn't write it down.

Sorry this is such a dump of information - so many problems and I'm not sure what is most relevant.

Other notes: my system is not finding any system restore points, so the easy option isn't there.
Outside of the incomplete updates from when I powered down (can't figure out how to maybe get it to complete that update...), the only two changes I had made to the system prior to the crash since I last turned it on were installing a video playing program from ESPN, which I have since managed to uninstall from safe mode, and turning on the Vista spyware program (popped up from security center, suggesting I turn it on, and I did). Haven't been able to get into security center to turn it back off - security center seems to not respond when I click to open it.

Ok, serious information dump, but anyone who can cull through it and offer me any tips for next steps would be approaching hero status for me at this point.

Many thanks,
Doug

Looks like Dell is sending me a replacement hard drive. No need to respond to this thread.