Hi,
afaik avast can't normally delete files in System restore..
but if you disabled RESTORE incl reboot, then ALL files in it will be gone.. -> so a subsequent scan with avast won't/can't find anythign in it..
for additional safety, you could run an onlinescan from Trend (see below) and/or
www.ravantivirus.com after you've cleaned up your PC , you can reenable system restore, and set a new restore-point