h4x0r, after 10e^46578398239 blinks of the cursor on his windows 98 machine, managed to create something worth selling. Now, you would expect him to open source it but then how will he upgrade his Castle? Now you and I don't buy softwares do we? And this 'Enter the Registration Key' prompt makes you and I want to tear your hairs apart. Your job is to get that #$&%$##@ key. This should be easy for us but we want you to have the fun.
You can find the software here
The flag is the SHA-256 hash of the string obtained.