The worst must have been the volume with PeachyForum database, a few months back... lots of little files (attachments) and one big file not going anywhere. I just hate window file explorer, when I try open a dir with 50.000 subdirs and with 100 files/dir it takes about 5 min to load it.
The circle have closed... I nowadays use only DOS window to copy files and defrag drives every few weeks.
Btw besides defragmenting, enabling "write caching" on the harddisk's hardware properties makes it a bit faster... and removing indexing. I've even made a sata raid drive for performance, but can't say much difference to ata drives...