Rear gears don't turn anticlockwise I've taken the rear wheel off my bike but the rear gears are stuck and do not spin freely anticlockwise.

It had been out of use for about 4 days, kept in a dry garage. I took the wheel off because it was bent, then found this problem.

Any idea what's happened or if i can fix it?
Well, the freewheel/freehub is frozen, apparently.  Generally nothing to do but replace that component (repair is possible but difficult).

But there are two other possibilities:


Look between the big gear and the hub to make sure there's nothing (eg, a pebble) jammed in there.
The nuts on the axle (including some you can't see) may have somehow become overtightened.  You can try loosening the nuts you can see and see if that improves things, but you might as well take the wheel to your local bike shop since they have the tools to take it apart and know how to adjust it.