I can't run defrag on my computer.

I can run the initial analysis, which tells me I'm about 9% fragmented. I can also start the defrag process.

That's where it pretty much hangs.

I started the defrag one evening, and it looked like it was going slow, so I went to bed and left it on. In the morning, it was about 12% done. This was after about 10 hours. I cancelled it because I needed to use my computer.

I tried again today, and it was just as slow. In fact after 3 hours it was only 5% done.

What the heck is going on? I can't imagine it's really supposed to be this slow.

I have a 110GB harddrive and I have 56GB of free space left. I have 1.50GB RAM, and this is a Compaq Presario S6200CL Desktop PC with Windows XP Home Edition.

The longer you leave your drive without Defragging the longer it will take when you do, you could try a Third-Party Defragger like Diskeeper.

How long it takes depends on how fragmented the drive is and it's size. But it shouldn't take as long as you've indicated (though with a drive that size, with that much data, it is possible if it hasn't been done in awhile); there is probably something running that is causing it to restart. You can try to figure out what it is, but it's best to just boot into Safe Mode and run it from there. At least try that initially and see how long it takes, this will give you an idea of how long it should take when you try it in normal mode.

Is this 110GB all one partition?

I have a 110GB drive with 90GB free space and it took the built-in defrag program about 4 hours to complete. I purchased a third party program and it's been running on a daily basis for about 15 minutes. The more you do defrags, the shorter it takes to complete. I have mine automatically scheduled and it just runs in the background while I use the computer.

I hear tell when things get slow need defrag. I also heard on wery early system defag a waste of time?

It's a double edged sword.
If you do it often you use a little time frequently which may in the end cost more time than doing it infrequently.
But when you do it infrequently each time will take a long time indeed (and may in fact need several runs to fully complete).

If you play a music cd again and again it wears out. If you play your hard drive again and again WHAT?
thanks for repling so Quick .

The CD will only wear out if you have a very poor quality CD player. In a decent player it will not wear out as no part of the surface containing the data should ever make physical contact with the player itself.

A harddisk can indeed wear out over time. It's a mechanical device.
BUT they should be kept spinning permanently anyway because starting and stopping them is what does the real damage.
Operating systems typically spin up the disks when first accessed and then keep them spinning until you power down the machine.
Of course this can be overridden by powersaving tools (especially for laptops) but it's not generally recommended.

It doesn't really matter if the hard drive wear out. Computers in general are absolete after 2-3 years. You will most likely upgrade your computer and would want a higher capacity hard drive before your current ones wear out. I figure I'd defrag the disk frequently now and see better (faster) performance than worry about the long term effect.

Wrong. Many computers last far far longer.
I still from time to time use a computer I purchased in 1997, the harddisk dating from a year later.
My laptop sees near daily use and was purchased in 1999.
My current main system has components dating back from around 2000, though most by now are newer (2-3 years old for most of them). The oldest parts are the harddisks and the floppy drive.

We recently retired our oldest server at work, it was about 10 years old.