I always installed directsoft (and all other installable programs) under the program files directory, usually it is the default directory (for most software I came across).
I installed using the custom install option
I never tried installing it in c:\directsoft5 folder actually.
Maybe that is the thing, although I have installed a bunch of other older programs under program files.
Hope you figure it out, it's time to hit the sack in Sweden know

Just to point out, I do run english versions of XP and Vista.
Cheers,
/Felix