shutting down hasn't finished (2.1) my battery was getting flat so HTC Desire 2.1 decided to shut down. That's fine but the shutting down never finished. 

Put it on charger. And when clicking Power Off nothing happens. The phone is slow to operate.

Is there anything else I can do except taking the battery off?
A while back I read something that suggested this problem could be caused by a dodgy SD card. The suggested fix that seemed to work for me was to unmount the SD card and then power off. I have since bought a new SD card and the problem has gone away entirely.