Defrag or no defrag

Not sure if this was caused by defragmenting, but shortly after a defrag session, the Recycle Bin began to crash every time I would right click the icon.

Defraging does not destroy existing non deleted files but because it writes data to the drive will reduce the probability of success of a data recovery effort on files that have been lost. This is the same as any write operation that takes place after the data is lost. Defragmentation does have substantial benefits to the read speed of data because defragmented files are contiguous and there is not the lag time that occurs when the read head has to move to another track on the disc to read data. I would say that if coupled with a good BACKUP system defragmentation is part of a good policy for all systems.

Running WinXP and Diskkeeper for defrag. I backup monthly.
I have been following this defrag and backup policy since NT4 and never had a problem. I have also always used Diskkeeper, not that piece of stuff MS calls a defragger.

It all depends on the health of your HDD. I have experienced problems after a defrag, and so have others that I know about. But the problems seem to be related to HDD health, not defragmenting.

Defragmenting moves data from one part of the drive to another, it re-writes the data that is moved, so it is actually very good (refreshes it). But, if part of your drive is failing (bad clusters) data can become corrupt. So, if I am suspect HDD issues I ALWAYS back up data before attempting a defragment.
If your HDD is suspected of having problems, run chkdsk (scandisk) or better tools, after running it, it should be safe to defrag.

First, thanks for all of the input.

What are the reasons to defrag and the reasons not to? Pros and cons.

Pro:
After defrag, file access is improved over a a fragmented disk.
After defrag, there is less head movement which increases disk life span

Con:
Due to OS and disk vagarities and improper disk health, you may corrupt a file which may later lead to OS reinstall.

I used to be a fan of frequent defragging using Perfect Disk until I had to do several reinstalls because the corruption ended up being passed into several backups.

I still support defragging, but less frequent. I now only defragment when fragmentation exceeds 10% rather that 1%.

Many defrag programs will take all the boot files and move them to the beginning of the HD where the rotational speed is greatest. This speeds boot time, sometimes an order of magnitutde. The better defrag programs either use the MS volume shadow copy to hot process most files that are in use, or use their own hot processing and can defrag just about everything hot. With these programs you still have to do the occasional boot time defrag.

I am open to dissenting opinions.

The way I see it, if a HDD crashes, the chances of recovering a file are increased if the file is contiguous (defragmented) rather than scattered all around the platter. Correct me if I am wrong.

Also, due to relatively reduced head/arm movement over the long term, the lifetime of a defragmented drive ought to be higher compared to a fragmented drive. So premature hardware replacement costs may be avoided.

These days, intelligent automatic defrag seems to be the 'in' thing, with software that enables servers and workstations to autonomously manage defrag without human intervention. Lesser workload on the admin, and less time wasted defragging a few hundred PCs regularly..sounds like a good deal.