Why do I get the error "Cannot use file because it was originally formatted with sector size and is now on a device with sector size " when I move SQL Server's log file?

A. This only occurs with SQL 7.x, not 6.x. For performance/consistency reasons the log writes are aligned on physical sector boundaries. 95%+ of disks will have the same physical sector size, but if you try and move between different vendor raid systems, or utilise some form of NAS device then you may see this problem.

The only work-around is to re-create the log file on the new device and backup/restore the database.