AntiVira won't start

Hi
I have a slight problem with Avira Antivirus. I downloaded the free version, (which I was running previously when I got the virus "Additional Guard") after I got rid of the virus. Everything went fine by installing on my laptop, but then when I tried to run it, it just won't start! I'm thingking maybe the virus killed some important files that it needs to run, and therefore it doesn't start! Could you suggest any files that I need to get this baby running again? In the meantime I downloaded Norton's 90 day trial version, but I don't wanna do this every 3 months!! If you could send me a link where I can download the needed files, I would very much appreciate it.

Please reply to the above address (michael.entz@yahoo.ca)
Thankyou in advance for your quick response.
Mike