run your treadmill without walking on it. If it runs and doesn't blow the fuse, You have a worn belt and deck or you need to lube your deck and belt.
I have a video on this if you need.
http://www.mindbites.com/person/214-Mark
If the fuse blows right away when you turn it on, you have a bad lower board.
You can email me for more help if you need to.
markepeterson@austin.rr.com
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix gym/fitness equipment.