Never fear! There is generally always a way out of these situations, it just takes someone else to have the same situation to come to rescue!
So, what you will need to do is:
1. Reboot your PC. The reason is that it still thinks your Android device is still connected (you'll see this in Device Manager).
2. Once rebooted, connect your Kindle again via USB. You'll probably hear 3 tones (which means it recognized a device, but didn't load any drivers). In device manager, you'll see a device just called "kindle" with an exclamation point by it. At this point, you'll need to install drivers for it again. Pick "Browse my computer for driver software" BUT don't browse, just click on "Let me pick from a list...", and select "Android Phone" and then pick the newest "Android Composite ADB Interface" from the list. I think you may have 4.0.0.0 or something similar (you may have only a 2.x version possibly depending on which drivers you loaded to root your phone).
3. Once you've done that, you'll need to run the following:
Code:
fastboot -i 0x1949 oem idme bootmode 4000
fastboot -i 0x1949 reboot
Hopefully at that point, things will look rosy again!