[Al Skierkiewicz]

D,
MCM is the place to go for parts but you better hurry. VCR's are using less and less of these parts and they get harder to find everyday. Only use an equivalent part. O-rings and other substitutes produce too much of a side load on the fragile bearings and plastic pulleys. Many of the belts are square to produce two flat sides to the pulleys. Before you replace the belt be sure to clean the pulley with some alcohol. If the belts have disintegrated, then the lubricant in some of the sintered bearings has likely dried out as well. Light synthetic oil will help there. Also look for the black grease on sliding parts and see if it is caked. MCM also sells a little jar of that stuff too.
Before you put any money into the repair, check the video heads. First look at them with a bright light. If there is a trailing black smear on the video head surface, then the video heads are worn to the point that they can't self clean. If the drum surface is clean, check for tip projection. Gently slide you finger sideways over the tip of the video heads (the little point inside the recess of the drum). You should feel a slight "bump" if there is sufficient tip. If the tip is barely perceptible, the machine is not worth adding anything to.
Can you give us the model and manufacturer?