Usually, when your microwave oven doesn't work it all, the internal fuse (thermal fuse) is blown. This fuse protects both you and the oven. When it blows, you need to have a qualified appliance repair technician replace it.
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Here's the fuse, but there is a reason it blew: http://www.repairclinic.com/SSPartDetail.aspx?s=t-spacemaker-%3d%3di3322&PartID=3322
Usually, when your microwave oven doesn't work it all, the internal fuse (thermal fuse) is blown. This fuse protects both you and the oven. When it blows, you need to have a qualified appliance repair technician replace it.