HDD won’t spin up – data lost?

Hi there,
Any help would be great. As “usual”, no latest backup available. It wasn’t my system disk, but for some reason the computer did not recognise either disks.
With an IDE-to-USB interface I can access the data on the system disk and the other partitions. But my main data disk doesn’t spin up. Upon connecting to the mains-adaptor, the powerlight in the usb-interface just goes on and off, as the drive starts spinning, and is recognised, but half a second later it’s off again. I’m aware that there are options “out there”, but at the moment I’ve got a limited wallet, though I need access – fast.

I’d be grateful for any ideas.
Shorsh