I bet that you are trying to install a copy of W7 64 bit on parallels....
VMWare supports 64 bit OS also on Mac that would not be able to install it natively, due their EFI at 32 bit (an example is the mac pro 1.1, that has the EFI at 32 bit, while the following models has all the EFI at 64 bit).
I have W7 32 and 64 and i have no problems installing the 32 bit version on the mac pro, but i cannot install the 64, no matter what, unless i use VMWare
SocialC, your issue is basically the second issue that follows the one where you cannot start the installation that tokyoo mentioned; in some cases is possible to get a build of W7 64 that was modified, so it starts but when you reach the point of selecting where you want to install it, you get the error message that ask you for drivers, and you drive list is empty, even if you created a disk image or partitioned a real disk.
as far as i know, there is no way to fix this....is not Parallel's fault but the hardware and Apple that doesn't want to support 64 bit OS from M$ on old machines...some are able to install it using hacks or various procedures; i would suggest to save time and just use the 32 bit version.
My copy is a normal retail copy of W7; and the same apply for Vista 64; the 32 bit version works fine.