While Windows 64 is able to run 32-bit programs Total Commander should run as usual without limitations.
Currently a 64-bit version of Total Commander is not available.
That is because Borland has not yet published a Delphi 64-bit version nor is a 64-bit compiler available. That were a pre-condition because Total Commander is programmed in Delphi.
Most plugins are 32-bit DLLs so the programmers should have to write 64-bit versions, too. (What couldn't be expected since almost all plugins are freeware). Neverthless, in the transitional stage without working plugins the Total Commander would be not very useful for most of the user.
Besides, a 64-bit version would inflate the size of Total Commander without adding any functionality. Currently a filemanager could not derive a speed benefit from higher performance of a 64-bit system. So you could use a 32-bit version without disadvantages.
It incredibly was but it real. There are now 64-bit version of this program.