Protecting mah program

- I have written a program, I want people to pay for it
- It is a type of program I don't expect hackers to have motivation to hack (it's a recipe program)
- If the program doesn't receive a valid activation key, it goes into limited trial mode
- The activation key is the SHA1 hash of the installation key + a guid I picked.  They must enter this key to get out of trial mode.
- The installation key is the SHA1 hash of the hard drive model + serial number.  They get this and must email it to me with money.
- I don't expect typical users of this program to know how to spoof the HD serial number (lol females).
- Did I do this right?  Suggestions?

OP here.  Let me tell you what really justifies me charging for this program.  Honestly, it's just a front end to manipulate and change a recipe database in realtime.  I have the database persisted to a plaintext format for easy parsing and processing using external utilites.  I didn't even store it in XML format so perl and unix commands like grep can process it easily.  I plan to make the specification for this format publicly known so anyone can develop programs to manipulate this database (known as a workspace in the program).

There are no secret or proprietary algorithms or anything.  It's just a manipulator and it computes costs of things, which are all trivial stuff.  Indeed anyone is free to develop a competing manipulator of said data.  Therefore by charging for this program I am not encroaching on the freedom of the community at all.  All they are paying for really is a polished front end.