Is there a way to force install to a drive other than C? I can't currently install because it thinks I don't have enough free disk space(which is true, on C), but there appears to be no way to direct it to a different drive.
If you're talking about the Curse Client, you don't have a choice.
If you're talking about the WoW client, you *do* have a choice of where to install. If you don't, temporarily move enough stuff to an alternate drive, install it to C:, then move the entire WoW folder to where you want it, and move all the files you moved before back to their original location(s).