Just read a few bytes from any *solid* :) HW address. Protecting application:

For DOS prgy:
1. read a memory segment, (any -hm- fixed hardware, like motherboard or bios, no hdds or some slot's cards)
2. and put the string to an environment variable, then
3. build the variable in program and check with string in env. var.

So, if someone knows that somethig like that exist, I'm here.

Of coarse, the bytes array must be unique for that machine where application is.

rgds.