is this some thing I should have? Avira AntiVir Rescue System
Not unless you have a serious malware infestation not fixable by the scanners you already have.
It's best downloaded to burn to a disk, using a clean computer, once the affected computer has been compromised. It is then saved as an iso and burned to a disk that can be used at boot in the sick computer.
Why not get it now, I hear you ask?
The file is updated regularly to deal with the latest threats. So to get it now, and use it in, say, 6 months, is not going to be so effective.