Seems to me that the JBoss tools look for the standalone.sh file in the folder ..\jboss-as-web-7.0.2\bin\. If you have a windows version (at least the windows version of OpenSCG http://www.openscg.com/), the *.sh files are not delivered, as they are useless on windows machines (instead the *.bat files are there). I copied the standalone.sh file into this folder from a jboss version that I have downloaded from the jboss website and eclipse recognised the jboss directory without any problem. Probably it's enough to create an empty standalone.sh file in the folder, as it shouldn't be read under windows anyway.
Nevertheless, I cannot fully confirm that this entirely solves the problem, because when I try to starte the server in the server view in eclipse, the server gives an error (An internal error occurred during: "Starting JBoss 7.0 Runtime Server". classToLaunch cannot be null).