Ok, I just got an interesting software:

hxxp://www.chromix.com/ColorThink/windowsdownload.cxsa?-session=tx:8477D52A7B1C4A4C25271B6405566AA7

Protection is User name + SN. If I hexedit the main exe, I can fine strings like "Demo mode" or "SN entered is invalid". But if I load this file in IDA, I get nothing. No Demo string, no invalid SN string.

Any idea what the hell is going on?