If your product requires the use of the internet, then you can generate a unique id for the machine and use that to check with a license web service.
If it does not, I think going with a commercial product is the way to go. Yes, they can be hacked, but for the person who is absolutely determined to hack it, it is unlikely they ever would have paid.
We have used: http://www.aspack.com/asprotect.aspx
We also use a function call in their sdk product that gives us a unique id for a machine.
Good company although clearly not native English speakers since their first product was called "AsPack".
