It's good to hear that it works!
Bad news for me is that it seems that my drives doesn't fully support the spindown feature (Seagate 7200.12), which means that when they spin up they will work, but start spinning down after 10 seconds of inactivity. A reboot solves the problem.
A good news for you might be that I found a more polished solution, called HotSwap!
. It's a freeware program from Japan, which does it all, and it has a neat clickable interface on the system tray. It supports spindown, unmounting, everything.
For HDDScan, you can put it in any folder, it doesn't need to be on the drive, and as far as I know it's portable (doesn't need to be installed, you can start it from any folder). But I would suggest for everyone to try out HotSwap! if it works on your system then it's a really cool one-click solution with no need for HDDScan or mountvol batch files.
EDIT: It seems that Windows 7's built in "turn off hard drives after ... min" works well on my drives, it must use a different command than what HDDScan and HotSwap! uses to turn off the drive.
Now my batch files are simply mountvol down - wait 1 minute - mountvol up, without the HDDScan part.
EDIT #2: Turning off HDD checkboxes doesn't work for me in SpeedFan, but I have found out that starting it with /NOSMARTSCAN option compeletely disables all SMART functions, hence it works very well for hard drives in a spindown.