While i was working on my other computer it turned off, i had been on for awhile so i figured it might have over heated so i left it alone for a couple hours. When i tried to start it it sounded like it was about to start up fine but then everything stoped and just the green light was left on. So i turned it off and tried powering up again, and now nothing happens except for the green light going on.
I hear nothing try and start not even fans.

This computer has been running for the past year without problems.

My only thought is recently i bought a new mouse and that probably uses more power then my previous one (both optical however) and that it burnt out the psu?

You might be thinking right about it being a power supply ,can't imaging it being the mouses fault though ,all you need to do is try a new PSU