Fn + Up/Down Arrow locks my tab button

[dmramsey]

Hello,
I have been having this problem with my windows vista that I have pretty much spent the entire weekend and every free second yesterday trying to figure out. First of all, I have a Dell Inspiron 1525.
When I turn my computer on and wish to adjust the brightness of the screen, I press the Fn button and the up or down arrow key. It had been working fine all the way up to this weekend. Now when I press the Fn + Up/Down key, it still adjusts the brightness but it also "glitches" and opens up what normally Alt + Tab opens up and starts continuously tabbing through my application list. After about 10 seconds of continuously tabbing through the applications list, the application list goes away but my computer continues to keep Tabbing. The tab button keeps tabbing no matter what application I have up. I have found only 2 ways to stop the continuous tabbing. The first is restarting my computer and the second is on a mouse I purchase (Gear Head Item #:MP3000WS) there is a tab switch button, I press that and it makes it stop. I have no clue where to turn since this is my first Computer and I am getting really frustrated.
If anyone could help me that would be greatly appreciated!

Thanks,
Derek