>Does anyone has a solution ?
>A better way of protection ?

You might think about a hardware solution such as the Hardware Keys made by companies such as Alladin, Software Security, etc. Pick up any C/C++ magazine and you'll see tons of ads for them. Plus less maintenance for you, 1 key = 1 operational copy of the software, if they want to install more sites, send them more keys, you don't have to be involved asking them to get you Bios numbers and HD numbers and the like...