Go to the start button, select Run, type in prefetch, click ok
When the screen comes up with a list, delete all of them.
This should reset the prefetch/superfetch function.
(see last sentence in next paragraph)
SuperFetch is implemented in %SystemRoot%\System32\Sysmain.dll as a Windows
service that runs inside a Service Host process
(%SystemRoot%\System32\Svchost.exe). The scheme relies on support from the
Memory Manager so that it can retrieve page usage histories as well as
direct the Memory Manager to preload data and code from files on disk or
from a paging file into the Standby List and assign priorities to pages. The
SuperFetch service essentially extends page-tracking to data and code that
was once in memory, but that the Memory Manager has reused to make room for
new data and code. It stores this information in scenario files with a .db
extension in the %SystemRoot%\Prefetch directory alongside standard prefetch
files used to optimize application launch.
I suspect you have a corrupt file stored in there.