This device is very old and it probably is in a rather old system. If Promise didn't write a Windows 7 driver, then there isn't much that you can do other than trying a driver from a previous version of Windows, but it probably won't work.
As much of an improvement Windows 7 is, it is pretty sucky with older hardware and software. If your hardware has decent Vista drivers available you should be able to use those, and I think you should be ok with the 378. I had a quick google and spotted some from Asus etc.
Fastrax 378, work for me on windows 7, mainboar asus p4c800e deluxe. I hope this is can help thanks http://www.station-drivers.com/page/promise.htm = FastTrak 376/378 drivers version 1.00.1.39 & 1.00.1.41 pour Windows 98/Me/2000/Xp 32/64bits new