If you have recently updated your Android SDK you will find this target;
id: 17 or "android-12" Name: Android 3.1 Type: Platform API level: 12 Revision: 2 Skins: WXGA (default)
You may be lured into creating an emulator using it. If you do, don’t expect it to work. I wasted a day on it. It goes so slowly that it is unusable. Adding more ram helps; hw.ramSize = 2047. Unfortunately on my Windows 7 64 bit box I got the error “Cannot allocate memory”.
Lots of users report the same problem. If you need to test on an Android tablet buy a cheap one and use that.