JoyToKey
JoyToKey is one of my favorite little programs for Windows. It takes input from gamepads and lets you assign keyboard/mouse functions for them, thus allowing gamepad support for games that don't have it natively, or further customization even for those that do. It's not a complicated program, but it does what it sets out to do well.
It's now a pay program, but if you search you can find older freeware versions--until finding their place on the web I was using freeware 3.7.4, but as of this writing they're up to 5.0. I paid, less because there are a bunch of amazing new features, but because I've definitely got more than $7 worth out of this program.