The brush doesn't spin anymore, but the belt is not broken. model DC 07; approx three years old

check and clean the brush bearings located on each end most reasons that belts break is the brushes are binding from debris --others bad belt or old and dried out

this is what is is broken it is the clutch Dyson clutch belt assembly for DC07 amp DC14 900252 04 473

most likley needs to be changed it is also a good idea to change the roller brush at this point also

Dyson Dc 07 14 33 Upright Models oem 904174 01

see this causes and fix it. God bless you
If the vacuum cleaner brush is not spinning, the brushroll bearing might be jammed. Try removing the brushroll assembly and cleaning all hair, string, lint, etc. from the brushroll bearing. If that doesn't solve the problem the brushroll may need to be replaced.
If the vacuum cleaner brush is not spinning, the brushroll assembly itself might be jammed. Try removing the brushroll assembly and cleaning all hair, string, lint, etc. from the brushroll bearings. If that doesn't solve the problem the brushroll may need to be replaced.
If the vacuum cleaner brush is not spinning, the brushroll itself might be jammed. Try removing the brushroll and cleaning all hair, string, lint, etc. from the brushroll bearings. If that doesn't solve the problem the brushroll may need to be replaced.
If the vacuum cleaner brush is not spinning the cogged belt might be broken, stretched out too much, or might have fallen off. Check the belt and replace as needed.
If the vacuum cleaner brush is not spinning the drive belt might be broken, stretched out too much, or might have fallen off. Check the belt and replace as needed.
If the vacuum cleaner brush is not spinning the belt might be broken, stretched out too much, or might have fallen off. Check the belt and replace as needed.

Remove the beater brush assy & remove the
shaft & brgs that go through it 7 clean out the
hair,fuss ect,so it will turn

You need to take your vacuum apart once a year or more
to clean things so they continue to work

Sounds like the brush that the belt is supposed to turn is bound up tight. Need to remove the brush and clean all debris from it. Where you can get at the center rod for the brush, the rod that the brush spins around, clean the ends and add some WD40, being sure not to get it on the belt. This should remedy the problem of the belts burning as long as the belt is put on correctly.

You need a new belt.

This model has Brush Control
The Brushbar can be turned off to protect rugs and delicate floors
You've either accidently turned the brushbar off or the belts broken

Don't worry it's probably just that the belt has broken or stretched. Your actually supposed to change them yearly. So if its been three years thats probably the case. Here is a link to the belt you need and a manual with instrutions:

Dyson DC07 Belt and Manual

The belt that drives it has probably broke,If you can remove the head on that model remove it and replace the belt . You make have to access the belt by removing the screws from the bottom of the power head.

belt doesnt have to be broken, check the metal arm on the vacuum, see if there is build up of old rubber from previous belts, clean the arm that spins the belt and double check to make sure u have the correct belt