Everything I had posted here before is now outdated (and more than likely was when I came up with this). The latest Xinput driver from Microsoft supports the Harmonix controllers out of the box (people who think I'm fake probably already had this). You can get the 32-bit version here and the 64-bit version here.
Be sure to check out Andrew Rudson's Drum Machine
Answers to common questions:
Does this work for PS2 or PS3 controllers? No. This driver is for Xbox 360 compliant controllers. Seeing as I don't have either of those, I don't know their level of support.
Do the Xbox 360 work on the PS3/PS2 version (or vica versa) More than likely not, but once again I don't have anything to test it out with.
You're not a hacker. I plugged mine in and it just worked. Not really a question, but: A) I had old drivers when I did this (Nov '07). The old drivers didn't support anything outside of Microsoft Xbox 360 controllers. The newer drivers have been rewritten to support third party contrllers.
B) Hacker is (or was) a synonym for programmer, so once again, you're wrong.
I have a problem with my computer. Can you fix it? Being a full-time college student I don't have time to attend to every little problem. There's an internet full of willing people who are much smarter than I and have far more time.
No time? But you made this! You obviously have no life! I made this in half an hour (video included). And it was over Thanksgiving break at that. You, my fine sir, troll the internet telling people they have no life when it is in fact you that have no life. Seriously, go and get yourself a girlfriend. Once again, you lose.
Okay, enough poking fun at people. I hope this brings all the confusion and chaos to a close.