Failure in Microsoft Update

I have Gateway Pentium 4 computer running Windows XP Pro. It got infected with Virus call MS Blast.

I downdowned Virus Removal Tool from Symantec’website call “FixBlast”. It cleans the virus.

Then I download Microsoft RFC security update. In the midddle of updating error message occurred stated “Could not verify the integrity of the update.inf. Make sure the Cryplographic service is running on the computer.”

I checked & found Cryplographic service is running

How can I get through this.