1. you can't delete from the system volume information folder (whether or not you can see it), it is a protected storage area and the only way to get rid is to disable system restore and boot as I have said!
2. delete is never the best first option, it's final, move to the chest where it can do no harm. It can be restored or deleted from here after a week or two. Didn't avast give the option to move it to the chest?
3. a google search returns lots of hits for mail.exe, some appear legit however, you would have specifically installed a program that uses this.
There are also suspicious hits also such as this one
http://www3.ca.com/securityadvisor/pest/pest.aspx?id=46273 were it is a mailer to send email with forged headers (spam or infected emails?). You have to do the analysis and decide.
With that many viruses your system cpuld well be seriously compromised and I suggest you also run hijackthis and get an on-line analysis of the log file.
Program & Tutorial - Also useful as a diagnostic tool - Download
HiJackThis.zip - HJT Information
HiJackThis TutorialFor an on-line analysis -
HiJackThis Log file - On-line AnalysisIgnore any 023 reference to avast processes, this is a hiccup in the HJT 1.99.1 (especially missing file entry for avast), if you need any help with any of the analysis let us know.
If you haven't already got this software (freeware), download, install, update and run it.
1.
Ad-Aware2.
Spybot Search and Destroy3.
Spywareblaster