You don't.  Instead, avoid calling STA COM components from non-STA threads.

David

The crude way (that lots of people will probably jump on and say "don't do
that") is to call Application.DoEvents every now and then while you're
reading files (e.g. once per file).

The right way is to move your lengthy processing to a worker thread.  Use
async delegates, the thread pool, the new BackgroundWorker (2.0) class, or
the System.Threading API directly.  Be aware that once you move processing
to a worker thread, you need to marshall all UI access into the correct
thread using Control.{Begin}Invoke.  It's not allowed under Winforms 2.0 for
a thread other than the owning thread to touch any GUI compoent.  (It was
allowed in 1.1 and before, but there was no guarantee that it would work,
and it's prone to deadlocks.  This is a core Windows limitation, not
anything specific to Winforms).

-cd