Left mouse clicks will not register in some programs/applications

I have a Dell Percision T7400 desktop workstation using the install disks provided by Dell for my system. About 9 months ago the system stopped seeing left click requests for some applications.

At first it was just in Firefox, I would have to leave the application and go back to it to be able to click on any links any time I navigated to a new page. Drop down menus don't work with the left mouse button at all.

I switched to Chrome, and I was unable to enter any of the contextual Chrome menus via left click no matter what I do, but clicking links works properly.

I have issues within some Windows configuration programs that require the same action as Firefox (swap out, back in) or do not see left clicks at all.

Today I formatted and re-installed Windows XP Pro SP1 from the disks. During the install process, it would not take left clicks for date/time/region settings, it would not take left clicks when I got to the "Next" and "Finished" prompts right at the end of the Windows setup.

I still have the exact same problems as described above on a fresh Windows install with nothing but Firefox, Chrome, Windows Live Messenger and Skype installed.

I have tried 3 different mouse brands.

I have uninstalled the mouse drivers and allowed Windows to put back a default.

I have run sfc /scannow to verify that Windows was not corrupted in any way.

Please help, this is extremely frustrating. I figured a fresh install would solve the issue, but no dice. Thanks.