Computer (Windows XP) Problem

[Cptn Patches537]

Hello all, hoping the strategy of combined knowledge and experience can yield some answers here.

The Problem: Windows XP will not start, I receive an error saying there is a "Bad Image Checksum" or something..related to the file secur32.dll

This resulted from the windows update from SP2 to SP3, which caused some crazy conflicts with Threatfire, AVG Free, and Firefox...basically firefox wouldnt start after the update because apparently Firefox 3 and Threatfire arent compatible...and in deleting Firefox to attempt a reinstall..somehow said file was lost or corrupted.

What I have tried: I attempted to boot windows off of a windows boot/update disk to recover the lost file through the recovery console HOWEVER...prior to the screen giving the option to select recovery console I receive an error claiming that my drive may be infected and that I need to run the CHKDSK function.

The error code is as follows STOP: 0x0000007b(0xF78D2524, 0x00000034, 0x00000000, 0x00000000)

From what i understand...CHKDSK cannot be run until the recovery console is reached...

I read somewhere that to do this would require transplanting the drive into another computer as a secondary HD to run CHKDSK...at which time I would likely throw in the towel and take it to a professional

Comments? Questions? HELP?

Thanks in advance for anything....Larson