Pete's QBASIC Site

I am worling on a VBDOS program and want it to be Shareware. However, I can't do conditional compilation with VBDOS. I thought about using a password to enable the Registered version features like other programs, then encrypt it with such computer-specific information such as the containing drive's serial #. But what if the computer's configuration changes? BTW, this program is supposed to work in a network environment. Also, how do I access said computer-specific information from VBDOS?