cisvc.exe is the Indexing service.
If you are using Windows 2000, make sure that you update to SP 4, to
eliminate excessive disk flushing that was experienced with SP3 version of
that service.
Whis is occuring otherwise is that during idle time, the indexing service is
updating the file indexes that it maintains about the files on your machine.
This service is designed to "yield" to other processes that ask for
processor time so that it doesn't impact performance.
You can of course turn off the Indexing service by opening the Services
applet or Computer Management applet in the Administrative Tools for your
machine (of course you must be logged on with Administrative privileges) and
find the Indexing Service. Open the service settings by double clicking on
it and set its Start Up Type to "Manual" or "Disabled" rather than
automatic.
HTH
Steve Arbaugh
MS Access MVP