marine80........ How many running processes do you have? ....perhaps one is hanging up and slowing down the shutdown .
Yeah, I notice that if you have a bunch of stuff open when you shut down it will have to close them all first which means it uses the "End Task" function which, I've noticed, takes forever to end the task...Assuming you're on XP as am I.
Also, go with what was mentioned about startup programs. To see what it starting up when you boot up, go to Start>Run... and type in "msconfig" without the quotations. Click the "Startup" tab and see how many things you've checked.
Chances are: if you got your computer from a rent-to-own place then it will have a bunch of their programs on their for some reason. Unchecking some or all of these won't kill your computer but it may cause soem things to not run correctly or at all. All I have slected to startup is my Anti-Virus and Volume Control. Only have what you occasionally-to-always use start up. Otherwise you're just loading programs for no reason which is a waste of RAM and CPU speed.
Not to mention, the more programs it opens at start up means the more programs that are open all together. The more programs which are open when you shut down, the longer it will take to shut down.
Observe your shut down sequence, too. See what comes up on the screen and relay that back to us.