what will you do when defragmenting your computer?

Since I use Diskeeper 2008 automatic defragmenter for defragmenting, I don't have to worry about shutting down other programs during the defrag :) I can use my computer as usual, and there is absolutely no problem. Diskeeper operates on the principle of intelligent resource utilization i.e. it defrags only with unused system resources. So, it never slows down the computer during a defrag- it will automatically suspend and resume the defrag according to available resources. I have tested this by leaving the auto defrag ON, while playing Mass Effect, Bioshock etc, and there is absolutely no performance hit :)

When we are defragmenting the drive in which operating system installed, then it was good if we close all the applications. Otherwise, this utility may fails to defragment all files properly. But we can use browsers for surfing as surfing don't take much memory in hard disk. But it effects you operaiton and some part of the drive was not avialable to this defragmenter. When we are defragmenting other drives, we can run any program. Be sure that the drive which you are defragmenting is not used by any program. That is only the thing behind the defragmentation.

Yes, when you are doing defragmentation, you should close all the application running. Close all the windows. And leave it idle for sometime. Though you wont face any problem in access any of the windows functionality even if you are accessing. So better leave all close all application while running defragmentation. I always do it.

I think defragmenting just require us to close programs like media player,or some office related programs but i don't you can experience any problem when browsing the while running some system fixing programs like disk defragment.Infact disk defragment is just to regroup files(fragmented) and puting together(defragmenting) so that your system can perform better

I don't think it really matters if programs are running during a defragmentation. The only effect I notice is that the defragmentation takes longer to complete.