Hi Sparkey,
From the location that you gave the file was in one of the folders used by System Restore to attempt roll back, etc. 'C:\System Volume Information' and the sub folder _restore, one of the restore points.
Anything removed from here, virus or otherwise could make this restore point invalid or possibly corrupt. Forcing you to go back to an earlier restore point.
When trying to delete a file that is in the Protected System Volume Information folder (system hiden folder) you have to disable System Restore, this effectively removes all restore points and you have to start afresh when you re-enable it.
I'm don't have a great deal of confidence in System Restore and I certainly wouldn't use it as my first or only line of defense to protect my system and settings, see below.
System Restore
There are many, many reasons why a System Restore may fail. For example, see "Why are previous restore points not working?" in the "Troubleshooting" section
of this official Microsoft page:
http://www.microsoft.com/technet/prodtechnol/winxppro/plan/faqsrwxp.mspx
There's lots more on that page that's worth reading too. Note especially the sections on "Does System Restore protect personal data files?" (the short answer: no); "What should I do if System Restore does not work?"; "Why are my restore points missing or deleted?"; "Why does the System Restore Wizard lockup?"; and so on. Just a few minutes on that page ought to convince just about anyone that System Restore is not intended for heavy-duty system protection!
More info:
http://www.kellys-korner-xp.com/xp_restore.htm
http://www.experts-exchange.com/Operating_Systems/WinME/Q_20718080.html
http://www.google.com/search?q=system+restore+fail
It is most likely that the second file, when it was deleted by avast it could have been saved into the restore point, because it was in the windows folder and this is one that system restore protects, sic.
You may have to bite the bullet and disable System Restore and reboot, then enable System Restore. After all avast was removing a virus that would re-infect your computer if system restore rolled back to that point.
HTH David