Windows 7 x64 driver for Adaptec 2940 SCSI card
If you can find someone with a Vista x64 system there is an "Adaptec AIC-7870 PCI SCSI Controller (Emulated)" driver in the Driver Store on that system that will work with Windows 7. For some reason, that driver was dropped from the in-box drivers in Windows 7.
It is located in the C:\Windows\System32\DriverStore\FileRepository\djsvs.inf_6451fbc2 folder. Copy that djsvs.inf_6451fbc2 folder to your Win7 computer.
To install it, go to Device Manager, select your SCSI adapter, right click and choose Update Driver Software. In the Window that appears choose "Browse my computer for driver software". In the next window, enter the location of the djsvs.inf_6451fbc2 folder on your computer, then click Next. You will get warnings about the drive being unsigned and that it may not work. Say yes, you really do want to install the driver -- it will work.