My Escort Mk4 XR3i refuses to move...

When I put it into gear, I get nothing but a nasty grinding noise.

The clutch appears to work, as I cannot put it into gear without using it and the nasty noise stops when I push it in. The car seems to go into each gear OK too, but I get no drive.

The gearbox itself is fine too - it worked in the car I got it from and nothing has changed, just put it into this car.

I'm at a loss as to what the problem might be - any suggestions?