system
2
Hi,
please give the exact message(s), especially full path/folder/filename of the missing files
did you detect/remove a virus recently ? if so, which ?
try avast Cleaner → www.avast.com
and use regcleaners to weed out obsolete entries in the registry
→ search this board or google for regClean

Which Win do you have ?
are all windowsupdates applied ?