Nikon does not support their Scan 4 software for 64bit Win7. Here's an article that explains how to overcomer this: http://www.colorneg.com/XP/Vista/7/driver_for_64-Bit_Windows/Coolscan/Nikon_Scan/
There is also a copy of the article stored at:
U:\User Data\LHF\12-09-03 Nikon Scan 4 install instructions