Windows Service Pack 2 Update failed

Hi,

I just upgraded from Servoice Pack 1 to Service Pack 2. My new trading
software provider's platform only works with SP 2.
After downloading (during which my spybot search & destroy program lamented
already all the changes to the register...) the computer does not boot up.
The message reads:

STOP: c0000221{Bad Image Checksum}
The image CRYPT32.dll is possibly corrupt. The hader checksum does not match
the computed checksum.

I cannot get past the screen and the system will not ocntinue to boot any
further...
Any assisatance would be great ly appreciated...