Is this an USB drive? If so, no wonder hdparm quits, because AFAIK it works on the IDE-bus. But "man hdparm"
Is there useable information when issueing "lsusb"?
Do you use the smart(cntrl) suite? (If not google for smart or go to sourceforge ...
) I don't remember but that might be able to do something.
Best bet is probably Maxtor as they have some free tools for their hardware. Go to their site (now Seagate?) and look for those, they should be able to control spin down behaviour.
Please come back and post your results.