windows security center/unable to download updates

Hello,
A couple of days ago I had a Malaware scare as I got a "malaware alarm". I went through the Read and Rund Me First and got great help to clean my computer. However, for 2 days now my Windows security center is no longer opening - I am getting the following message 'The Security Center Service can't be started"
I am also getting a message saying I have an important update to download. I try downloading but it stops quoting error 80070643. I've followed their steps to restart the Office Source Engine (OSE) service but id doesn't seem to help.
The person in the Malaware forum suggested I contact you if the problem continued.
This is a brand new computer (3months) it is running on Windows Business Vista and I am still using my Windows XP programs.
HOPE YOU CAN HELP ME!!!
Joanna