I believe I've got good news about running a Nikon Coolscan ED4000 to run in Windows 7 x64.
I found Bob Johnson's website, and a page called 'Getting a Nikon Scanner to Run on 64-bit Vista'. It's at: Getting a Nikon Scanner to Run on 64-bit Vista - Photo Tips @ Earthbound Light
I followed his instructions exactly: downloaded NikonScan 4.03 for Vista x86, and installed it in compatibility mode in Windows 7 x64, using 'Vista SP 2' as the OS it had worked in.
Then I copied/pasted his 'scanners.inf' file (on his webpage), and put it and 'NKScnUSD.dll' in a new folder. NB: He says you find the .dll in "C:\Program Files (x86)\Common Files\Nikon\Driver\Scan1394", but mine was empty. It was in "C:\Program Files (x86)\Common Files\Nikon\Driver\ScanUSB".
I turned on the NikonScan, opened Device Manager (the Nikon Scan was listed, if I remember right, under 'Other Devices' - it's now under Imaging Devices, so I can't be sure of the exact name), and followed his instructions about installing the drivers from my new folder.
It worked. I've just scanned a slide - in Windows 7 x64!
(I also found a workaround that involves installing a program called Vuescan, copying 1 driver, and uninstalling - it's at Manual Focus Forum / Nikon Coolscan Scanner and Vista 64
. But Bob Johnson's workaround seems simpler.
Hope this works for you.