Cannot download Avast

I’m attempting to download Avast because I have a virus. Every time I try to install, I get a “avast has stopped working and will shut down” message. My OS is Vista. Please advise.

You probably have a virus that is killing your AV, I assume that the same was happening to your original AV before avast ?

Bagle Rootkit variant:
See http://forum.avast.com/index.php?topic=26554.0
http://forum.avast.com/index.php?topic=25941.0
This seemed to have the best results with this type of attack and is reasonably user friendly.
http://research.pandasoftware.com/blogs/research/archive/2006/12/14/Rootkit-cleaner.aspx
Also F-Secure Blacklight may not always be available, http://www.f-secure.com/blacklight

Thanks.

Your welcome, there was a sneaky question in there about previous AV and if it happened with that ?