i have passed from Vista 64 bits to Windows 7 64 bits
I am using many 2d-3d softs, some installed on my D drive ,others on my E drive ,none on my C drive (where i have only Os and some utilities like antivirus,defragmenter,hd image backup ,nero)
I am using some 64 bits softs (like Lightroom 2 and Vue 8 infinite ) and many 32 bits graphics softs
Everything works fine