If avast has been able to move it from the C:\System Volume Information folder, in the past it wasn’t able to do that but I believe it now can.

Confirm it has been moved and if so you could leave it in the avast chest for a few weeks, a protected area where it can do no harm and scan it again in the chest if still detected then delete it.

Personally I would suggest you disable system restore and reboot, that will remove ALL restore points, infected or otherwise. That way there is no possibility of at some time in the future using system restore only to infect the system.

Win XP-ME - How to disable System Restore

After you have done that run another scan and if clear (you should be) enable system restore again.