"ScrewME #2" by Dynasty

[difficulty: 4] [protection: obfuscation, custom serial routine]

This has some anti-debugging tricks obscured among junk/obfuscation. The parts that verify the serial, however, are plaintext and viewable in IDA, so you can breakpoint there without stepping through the nonsense. I included a single-stepping program to attempt a more general counter to the problem of "finding the algorithm among the hay stack". An experienced reverser on crackmes.de, HMX0101 rates the difficulty at just 1 or 2.