Changing the path to a website in the Home Directory path won't cause the worker process to restart. It will however cause the Application Domain for the website to tear down and restart.
Worker process restarts can be caused by a number of events, most commonly:
If any of the conditions
on the Recycling tab of an
Application Pool's properties are
met.
If CPU monitoring (in an application pool's properties Performance tab) is enabled and one
of the monitoring thresholds is met,
and, if the required action is set
to Shutdown.
There is a catastrophic error such
as an unchecked exception thrown by
your code on a different thread than
the current request thread.
IISRESET
You manually force a recycle or stop and start the application pool
It should also be noted that an application pool recycle is different from a restart. When an application pool recycles, IIS starts a new worker process. All new requests are sent to this new process. The existing worker process is kept running but will be torn down after all outstanding requests are completed or the shutdown time limit is reached.
Existing ASP.NET sessions are retained in the old worker process until they are abandoned. This ensures ASP.NET session state is not lost upon a recycle, i.e. if there are still ASP.NET sessions, the requests matching those sessions will be routed to the old worker process. Classic ASP sessions are unfortunately lost because ASP doesn't have this same capability.