"Missing CD-Rom driver" halts 64bit install

[sgmidf]

I have an X61s on which I did a clean install of Windows 7 32 Enterprise on a blank harddrive. That install went beautifully. I want to try the 64 bit version but when I try to install it, it says that I'm "missing a cd-rom driver" and it can't find it even though I have Win 7 32 and SWTOOLS on the harddrive.
Can anyone help? I'd really like to use the 64bit version. I tried to search but could find this addressed.

Thanks