Wireless Mouse Died - light not on - new batteries - still nothing....

I have a Vista all in one wireless system that I bought in May 2008.  The mouse just up and died two nights ago.  I'm going nuts running my finger over that tiny square thing trying to move around the screen.  Do I just need to buy a new mouse or is there something I can do to fix it? 

I'm sorry, I don't know ANYTHING technical about how the insides of a computer works.  So if you are kind enough to answer this thread, please use really small words and directions that are easy to understand!  Thank you.  Sharon