That problem can be caused by the belt being stretched out and even though it is spinning when you look at it, with the resistance of the carpet it will stop.

With a model number I could tell you exactly how to change the belt, but most of the whirlwinds I've seen are similar.

You need to gain access the belt and roller. On most models there are two screws on the top of the nozzle inside one of the four indentions that run along each side. Once you take those out it allows you to take the hood off.

Remove the brush roller and old belt. Wrap the new belt around the motor shaft and place the roller through the belt loop and use the roller as leverage to stretch the roller back into the roller housing. It will take a little muscle. Give the roller a spin by hand before putting the hood back on. It should spin easily. If it doesn't then you might have pinched the belt and need to free it or the belt will just burn up when you turn the unit on.

A clog in the hose going down to the nozzle would also cause this problem, so check that hose when you take the hood off.

Modle 3272 how do you get the hood off i dont see any screws