>Hi hilmar
>can you guide me about a good copy-protection system?
>i have a very good system .but it is a DOS executable.
>i have source of this exe in pascal.but i can not change it to windows program.
>can you help me?

Well, I am no expert in this; my programs have been for use within a company, and I didn't have any need for copy protection.

Anyway, I will try.

First of all: Legal protection is very important. Microsoft used to have technical restrictions to copying programs, but those were bypassed in many cases. Nowadays, Microsoft relies mainly on legal protection. (It seems they are starting to use some technical copy protection again.)

I think that any protection you use can be bypassed; it can simply make the job a little more difficult for pirates.

Some threads were copy protection were discussed include:

Thread #784667
Thread #730926
Thread #726707
Thread #721374
Thread #720045

I will leave it up to you to see if you find useful details in these threads.

It seems to me that the best option is to buy some ready-made software-protection solution. But remember, no product can give you complete protection. Software on disk can always be read and decompiled or disassembled.