Vista problem

new day....new problems.
My church just purchased a new HP laptop to run our songshow and presentations at church. It has an Intel dual-core processor and 2 gig ram, with Vista Ultimate.
After bumbling around trying to figure out using Vista - I had the same problem come up twice - and I've only had the computer a few days!
When I am finished using the computer - I go to the Start button, find the "shut down' button and click it. And nothing happens. The computer sits there merrily NOT shutting down. I gave it a good 15 minutes to do so....but nada. I cannot, however, go back and try again, for the computer is obviously busy doing I know not what. I have to manually force it off.

Could anyone let me know why this might be happening?

Also....it might be just me, but the computer seems to be very sluggish and slow.
Is this normal? How can I improve the speed?

Thanks for any help you can provide...

Trish