Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
The solution that you should try first, is that the belt might need readjusting and lubrication (with the special, non-grease, lubricant these treadmill belts generally require.)
The belt should be adjusted, generally speaking, so that it is loose enough that it does not quite slip, but nearly that loose.
If the belt is adjusted (or, has shrunk up with age, and lack of lubricant...) too tightly, then it can stop the treadmill from working or running. An over-tight treadmill belt can cause wear, or even damage, in many other ways, such as by overheating the motor.
After that, it would be necessary to identify where the noise is coming from in the machine, even just generally in-the-vicinity-of, and also tell whether the noise is continuous grinding (possibly bad bearings or dry bearings), or an intermittent squeak (probably a loose part whose fastener needs tightening) etc.