To reset Dllhost you have to stop IIS either manually or by using iisReset utility. You may even stop Dllhost in the Task Manager -- anyway it stops or crashes your web app completely.

It may be even VFP COM object, the way it's coded, causing the Dllhost consuming all available resources of a server.

"dllhost iis" search in Google returns several helpful links:

http://www.experts-exchange.com/Operating_Systems/Win2000/Q_20230858.html

http://www.webmasterworld.com/forum47/1003.htm

http://www.cpcug.org/user/clemenzi/technical/Databases/Testing_w_IIS.html