Saving myself from Nookish disaster

To do a hard reset, turn off your NookColor. Then, hold down the Home Nook button and then press the power button at the same time until your machine powers back up and gives you a choice to reset your nook. Power button will cancel it and the Nook home button at the bottom will continue with the reset. Confirm it and it will take a couple minutes and your machine will be back to square one.

edited from: http://forum.xda-developers.com/showpost.php?p=9568755&postcount=4

That reset will clean out all your data, but it will not fix a messed up operating system.

If you also need to fix the whole operating system at that point, it takes a bit longer. You need to power up your NookColor but only until you see the first text come on the screen, then press and hold the power button for a count of 20 to stop the boot. Repeat 7 more times, and then your Nook will reinstall the original operating system.