Indeed, ideas can't be copyrighted. Blocks of program code can be copyrighted, though.
The simplest way to copyright a program code is the same method that other writers use, songwriters, for instance. Post a letter (by registered mail) to yourself with the work enclosed & once you get the letter back, keep it in a safe place, unopened. The date of registration is good in court, as the post office (Royal Mail, in the UK) keeps proof of the date posted, if it ever gets that far!
I, too, would consider it a compliment if someone ripped off a design of mine!
The best thing to do would be to come up with a completely original idea (or an extension/redevelopment of an old idea) & keep quiet about it! That way, you'll, at least, have a head-start over the competition. If you need to discuss your idea, publicly, then limit your discussion to
only the section of your idea that you need help with - don't give it all away.
Good luck.
edit: Soapyfish, did I nick your idea or did you nick mine?
Maybe, great minds think alike.
I have an XP3000+, 1.5gb DDR333, a 6600GT and I'm programming 3k text-based exe's?!