Disable default start up system

Question

I installed Windows 7 64 bits with Boot Camp and all works fine: when I restarted my Mac, it starts in the last Operating System I used:
- When I was in Windows, I restarted and Windows starts automatically.
- When I was in Mac OS X, I restarted and Mac OS X starts automatically.
But I made a mistake: I selected restart in Mac OS X from Boot Camp Control Panel. Since this moment it always restarts in Mac.
I have to press Alt key when I restart Windows in order to restart in Windows, because if I don't press the Alt Key, Mac OS starts as default.
If I change in Startup Disk to use Windows as Default Operating System, it happends the same, I can't restart Mac if I don't press the Alt key.
How can I disable default Operating System in order to start with the last started system?
Thanks.

Answer 1

If you want other applications to remain the default, for example opening up
an image, you can do the following:
Step 1. Click on Start;
Step 2. Move the mouse to All Programs and click on Windows Explorer;
Step 3. Find an image that is the type you want to open with OTHER
applications;
Step 4. RIGHT-click on the image and choose, "Open-With"... if you check the
box that says "always do this"... it will stay this way.
Cheers