There might be several reasons why you need to use a form, generally because you need to convey more information about progress than you can with a progress bar. However, as vladk quite rightly points out, most apps use a progress bar, and may also use a status bar to show what the last activity was.
If you indeed need to use a form, you can "set the priority" as you say, to the main form by using the setfocus method. Just say frmMain.SetFocus, and frmMain will have the "priority". We normally say focus instead of priority, so if you want to read up on this concept, read up on focus.
That said, you won't be able to use the main form while your process is executing. This is because processes are synchronous, so your app will work on your process until it's done, and put everything else you try to do in a queue which it will execute when the current process is finished. If you want to have your process run in the background, and use your form while it's running, you will need to set up an asynchronous process. The easiest way to do this is with events; this should work for you just fine. (A more complex way to do it is with callback procedures, this gives you more control of the interaction of the foreground and background processes.)
MSDN doc has a great example of this, using a coffee pot analogy. You want to start the coffee, do whatever you feel like while the coffee's brewing, and then get notified when the coffee's done so you can pour yourself a cup. If you work through this, and read up some on asynchronous processes using events, you should be able to put it together.
HTH
Bob
