I just bought a troy bilt self propelled mower last weekend. Everything worked fine. Although one week later it won't self propell at all. What could be the problem?

It could be that it is already broken. The motor that actually makes it propel itself could have already died out. In other words, it could have been a 'dud'

Hi,
If it is one of those variable speed models, put it in the highest speed to see if it decides to work. Some can become jammed if shut off at one setting and then have the setting reduced.
Peace,
Clarke

If it's one of those variable speed models, pop the plate in fron tof the engine (2 screws, I think) and inspect. Particulatly, the bushings can be worn.

Another problem with propeling, is if the wheels don't have any tread.