Slow Shutdown

My Mac (Snow Leopard.) is very, very slow to shutdown, which is most annoying when I am waiting to turn the power supply off. Can anybody advise why this is the case and whatI can do to fix the priobelm, please?

My first thought is there is a third party program or daemon running that is either out of date or broken and is causing the problem.

Boot to "Safe Boot" mode first. (Boot holding down "shift").

Then try powering the mac off. If it is much faster, you'd want start looking at login and startup items that are running in the background.

If it's just as slow to shut off in safe boot mode, perhaps there is a failing HD or you need to repair the file table with Disk Warrior, etc etc.

Also, if you have external drives that can slow down shutdown as the drives have to be unmounted first. And all open applications need to be closed, which can, if they have files on the external drives open, slow it down even further.