Don't worry too much about a detection in "system volume information". It can only become active
if you use system restore.
(To delete all restore points, and any trojans in them, turn off system restore, reboot, turn it back on. This should
only be done if the computer is running well.)
Did you uninstall AVG? If not you need to do so, and to run the AVG remover, get it
here. (For most users it will be the first tool, 32bit windows.)
2 (or more)
resident AV's should not be run together. Sometimes it can be done, but usually there will be problems.
I recommend a demand scanner. Download
MBAM and/or
SAS. Both have free versions. Both can be run alongside Avast, no problem. The free versions are demand scanners only; no resident protection. Both are very good at malware detection and removal.
Other tips:- Consider a two way firewall. The one I use is fairly easy to work out.
- Make sure your copy of Windows and all programs on it (Like Java) is up to date.
- Consider an immunizing program like
SpywareBlaster. This can block known bad websites.
- Clean temporary files regularly, say, once a week, or daily if preferred. Defrag every month or so.