From the name of the cab file, fs311.cab, I suspect that it is located in
C:\_RESTORE\ARCHIVE which is part of the system restore archive and has
nothing to do with the cab files windows\options\install.

I feel there is no need to be concerned about any virus or trojan in the
_RESTORE archive as they are harmless there and can only cause problems if you
later choose to restore to a checkpoint created AFTER infection and BEFORE you
cleaned your system. Something I hope you won't be doing after reading this
post.  Any worms, trojans and viruses in the _restore archive will
automatically be discarded in time as newer data is archived and older files
discarded  The problem with disabling system restore is that it flushes the
_restore archive and whilst that removes any virus remnants it also removes
any good usable checkpoints you might have and you never know when you might
want to use that lifebelt.

However If you are worried about this, then there are two approaches to
resolving your problem:
Firstly try reducing the space allocated to the System Restore archive as this
could flush out these unwanted files.  Do this using the slider found at
System | Performance | File System | Hard Disk and reduce the allocated space
until you flush out the unwanted files.

If that fails, reset System Restore:
System | Performance | File System | Troubleshooting and check "Disable
System Restore", Apply and IMMEDIATELY reboot.  This will flush you restore
folder and erase all checkpoints, then,
System | Performance | File System | Troubleshooting and uncheck "Disable
System Restore", Apply and again IMMEDIATELY reboot.  This should now
automatically create a new checkpoint immediately following the restart.
Finally adjust the space allocated to the restore folder,
System | Performance | File System | Hard Disk and adjust the restore slider
to your preferred setting.  A  figure of 200MB is normally more than adequate
for day to day use allowing perhaps a week of checkpoints to be available
although increasing this to perhaps 400-500MB for a few days during periods of
large installs such Microsoft Office is advisable.

See also MS KB 263455 - "Antivirus Tools Cannot Clean Infected Files in the
_Restore Folder" (http://support.microsoft.com?kbid=263455).
--
Mike Maltby MS-MVP
mcmaltby@hotmail.com