Yes. Windows and/or Mac
Yes, you can install and activate Creative Cloud desktop applications on two computers, regardless of operating system, for the individual associated with the Creative Cloud membership. See the product license agreements page for more information."
my desktop is a DOS based PC
DOS based? As in DOS from the 1980s? I assume you mean you're running a recent version of Windows.
Needs to be running at least Windows 7 or Windows 8.