When I set focus on a text box, on a forms load event in Windows Mobile 5.0, the Windows tool bar appears even though my form is maximized.
When I do not set the focus on the text box the form opens maximized. I do not want the windows tool bar appearing.
How do I prevent this from happening?
TThe start bar in WinMo is actually not part of your app - it is a separate process managed by the Shell and it really wants to always be on top. Trying to get your app above it goes against the design goals of WinMo (though it's a common thing to want to do).
I'd recommend doing some searching and reading on "kiosk mode" to garner what knowledge you can from others who have been down this road, but what you're seeing is that the StartBar is getting set topmost.
Raffaelle Limosani has a pretty decent blog entry that covers kiosk mode, so it's a good place to start (take a look at the other blogs he links to as well).
The toolbar at the top is actually a separate window, and it has a habit of appearing when not wanted over top of a full-screen ("kiosk" mode) app. For example, if you ShowDialog a second full-screen window from the first, the Start window flickers up for a split second before going away.
The only way I ever found of dealing with it was to hack into the API and actually make the Start window hidden while my application was open. This is a big potential problem, because if your app crashes without making the Start window visible again, it will stay invisible until you reset the device (or run you app again successfully).
I'd advice against doing this unless you absolutely have to. As ctacke points out, this would be an example of an app not playing nicely with Windows Mobile.