There is currently a problem with R12 where the SDK location cannot contain any spaces.
The default installation location is: C:\Programme Files(x86)\Android\android-sdk
. They are currently fixing the problem but you can currently work around it by changing the SDK location path in eclipse to C:\PROGRA~2\Android\android-sdk
.
If you are running 32-bit Windows, change the path to C:\PROGRA~1\Android\android-sdk
.