I have the bagless hoover windtunnel and it doesn't pick up anything and it is very hard to push. Changed the belt and The rollers are spinning and the filter has been changed. What else can I do?

nylon belt in center of brush underneath . not a hard belt change.

check the belt of the brush roller. Or check for a clog

The belt that drives the brush roll has broken. That's why it doesn't pick up and why it doesn't pull itself forwards. Check the User Manual (download from Hoover website if necessary) for information on replacing the belt. Good luck!

Turn the belt inside out. This problem stems from a design flaw in the mechanism that turns the hoover from bare floor to carpet. After taking it apart I realized that the spring that pushes the belt tight (to make roller spin) is not any where near strong enough to keep the brush rolling. My solution was to turn the belt inside out (there by essentially shortening the belt and allowing enough pressure to be applied to the roller to keep it spinning. Horrible design flaw. I am an engineer and find this pathetic. Hope this helps someone.

I would try changing the belts. You can get the belts you need here:

Hoover Windtunnel Replacement Belts

If you turn the vacuum so the bottom is facing up you will see the base plate that covers the roller brush. There will be four screws (usually phillips head), remove the screws and the base plate will lift off. You now have access to the roller brush and belt. Lift the roller brush up and remove the old belt. Place one end of the new belt over the motor shaft and the other end over the roller brush and put the roller brush back in place. Now simply replace the base plate and you're done! This models requires Hoover belt # 38528033 (single) or Hoover belt #40201160 (2 pack). You can get this belt at www.vacbelts.com.

Here's the pages:
http://www.vacbelts.com/hoover-40201160-belt.htm
http://www.vacbelts.com/hoover-38528033-belt.htm

Hello,
I see your question is from July. I just joined Fixya this month so wasn't here to answer. If you're still looking for an answer:
It sounds like the belt is broken or stretched out so much it isn't spinning.
I would suggest replacing the belt and also check the roller brushes for wear and replace if necessary. Here is a link to an online guide with illustrations to change belt and or brushes. Hope this helps.

http://www.info-vacuum-cleaner.com/hoover-vac-belt.php

The Hoover Windtunnel™ Self-Propelled models have two belts, a flat belt and the V-Belt. This V-Belt is the one that drives the Brush Roller. After about three months, most belts stretch out causing them to slip. This means the brushroll turns slower or not at all and the self-propelled becomes increasingly harder to push. It is recommended that both belts should be changed at the same time.

you have a broken belt. look on bottom of vac remove screws until cover comes of. you will find broken belt inside. take that with you to get a replacement

I don't know how old your machine is, but the belt should be changed at least once a year and you should check to make sure the roller spins freely. There are bearings at either end of the roller and they will become contaminated with dirt and hair after a while and will need to be serviced. A new belt will help, but won't last if the roller is in need of service.