oki,
you have tried all these:
1. cannot restore files from chest as they are already deleted.
2. file recovery softwares didn't help.
3. system restore didn't help.
atm,
well I would do this:
back up all the important documents(including avast! full setup file). format the windows partition only, so that all other partitions are intact.
load up windows afresh.
install all the required softwares including avast!, go online and update all the softwares including windows.
get a good backup or drive image creating software, back up the partition on to a portable hard disk which I would not use to any other purpose but only for creating back ups every 3 or 7 days(depends on how much you use your pc).
be prepared for future. should there be any problem like the on you just came across, just restore the partition with the image(backup) of the partition.
thats it from my side. stay here for a few moments.. if any of my forum friends have any better ideas then please give them a try.
else you know what to do - decision is yours.
thanks
nmb