Hi Computer  Hope

Yesterday, I started my computer just as always; however, a black screen popped up saying that windows was not properly shut down last night - though I always do.  It gives me options of starting into safe MOD, using last known good configuration, and starting windows normally.  The thing is, a second after my choice, no matter what I choose, takes me to an error screen.  
The screen suggests a possible software/hardware PROBLEM, but I haven't installed any hardware for months, and I check for spyware and viruses nightly.  

I USE a HP RUNNING Windows XP, and if it helps, I've copied down the error here:

UNMOUNTABLE_BOOT_VOLUME

Techincal Information:
***STOP:  0x000000ED (0x823527B8, 0xC0000032, 0x00000000, 0x00000000)


I don't know much at all about computers.  If someone could talk me through a possible fix, it would be much appreciated.Sorry to double post, but I forgot some possibly needed specifications.

1.8 GHz P4  Processor
512 RAM Quote

Sorry to double post, but I forgot some possibly needed specifications.

1.8 GHz P4  Processor
512 RAM

Okay, it seems  my registry is corrupted.

I tried repairing using my Windows disk, but an error pops up after my computer checks the files and before the "Welcome to Set-up" window appears.

Is there anything else that may work?