Ok, in some applications (like winamp and opera) when i left click my mouse, it will right click instead. every other application works fine, windows included. I reformatted my system, and its still doing it. It does it with a different mouse as well.

any ideas?

Sounds like a pretty unusual problem. This definitely doesn't sound like a mouse problem since other applications are working properly, and you've already identified that fact. I'm not familiar with Opera, as I use Firefox, but what version of Winamp are you using? Is it the newest? I know that some people like to stick with 2.x

Try the mouse/mice on a different known-to be working computer with the same software. If they work as they should, then you may have a mainboard problem in your PC (fresh install of OS did not work). Also, make sure the drivers are correct and up to date. If the mice still act funny, it may be some weird compatibility problem between the software you are using and the hardware...

Me thinks it is a driver issue of some sort, though - just a hunch...

To me, it seems very unlikely that this could be a mobo problem. Most especially because you only have a problem in 2 applications. Switching the mouse out seems to support this, but you didn't mention the mouse connector type. Were they both either PS2 or USB? If so, you could try the other connection type, but I wouldn't get your hopes up.

Typically I would agree with the driver comment, but it's rare that one would need to change a mouse driver. I have always used the default Win drivers, unless my mouse has special functions requiring manufacturer's software. I still recommend trying the newest version of Winamp (it's free,) if you haven't already.