Moving HDD from Vista 32bit to W7 64bit

I am thinking of upgrading my Vista 32bit pc to Windows 7 64bit to make use of the full 4Gb RAM that my system has. I have 2 disks installed and one has a lot of data files on it. Can I remove the data disc (it isn't needed to run my Vista system), do a custom install of Windows 7 64 bit, reinstall all drivers and programs, then plug the data disc back in and see the data? Or do I really need to copy all this data to another humungous external drive, do the upgrade, then copy it all back again as Microsoft recommends? I guess I really am asking if the two operating systems read write data in differing formats. Thanks for your help.

Specifically, can W7 64 bit read a HDD written by Vista 32 bit?

If I move the HDD from Vista 32 bit to W7 64 bit in this way will I see the best performance, or will it be compromised? I wonder if the W7 64bit o.s. would access the disc faster if it had formatted the disc and I copied the data back again?

No. Just leave the data disc alone as there are no differences to how either Vista or Win 7 see that second data disc. Just remove it from the system, do a clean install with format on the main drive for Win 7. Then, once you've installed everything along with all of the drivers (I recommend you go to manufacturer's website and download all of the Win 7 64-bit drivers for your system before you format the drive so you have them handy once it's done), just plug the data drive back in and you're set.

Wonderful. Now why couldn't Microsoft tell us that on their upgrade site - surely there must be plenty of folk with more than one HDD doing an upgrade! Many thanks for your swift help guys!

No problem. Make sure that second drive is not connected when re-installing the OS on the primary drive as the installer often writes a 100mb partition to a second drive on the system if it can (which you don't want/need).