Perhaps if a grab both ends of the stick then I'll be half right !
Seriously though.
A couple of things to try...
1.
Check to see if the date of the SHIII exe file is nice and old, not like last week of something. That would cut out questions about tampering.
2.
Perhaps your have a cluster problem with the drive, Do a Scandisk (in tools / properties of the drive) and check for errors. If it finds some then you need to consider replacing the damaged files with good ones (from your regular backup
)
Hope it helps.
Steve