Connect a Lacie Thunderbolt only drive to a USB port? I have a huge Lacie Thunderbolt only drive and I want to connect it to pre-thunderbolt computers but no matter where I look there doesn't seem to be a device or adapter which can achieve such.  

I've looked at Lacie, Apple, and all over the internet but nada, nothing, zilch..  Rather than toss the drive in the attic I'd like to give it some new use but the machines it will connect to don't have a thunderbolt.  Newer drives at least give you the option of using both but I was wondering if anyone out there might have some suggestions.
Thunderbolt is PCI express, so you would need an older machine to have a PCI express bus or card and then add an adapter card which would cost far more than a new USB drive.

I don't think that adapter (which is eminently makable) would be brought to market due to the cost of the "solution" to be implemented.

If you need a drive that connects to old and new computers, perhaps trading your awesome Thunderbolt drive for a USB one would make sense, but you might instead put the files on an internet share to do short term sharing of the data.