Avoiding spin-up on external SATA drive

One of the things that drives me nuts about my external Seagate SATA drive is that while the drive does go into power-saving mode, many apps seem to trigger it to spin up, which pauses my system (WinXP) for several seconds during the spin-up. One specific app is Adobe Acrobat, but there are others.

Are there any backup apps that would also "manage" external drives so that they're only given a drive letter when the backup is actually happening, and then remove the drive letter when the backup is finished?