Unable to locate tools.jar

Yes, you've downloaded and installed the Java Runtime Environment (JRE) instead of the Java Development Kit (JDK). The latter has the tools.jar, java.exe, javac.exe, etc.

In case this is still an issue for anyone, I have a bit of clarification on the previous answers. I was running into this same issue using ant with only a JDK installed. Although, the JDK installer gave me a directory structure like this:

 Directory of C:\Program Files\Java05/08/2012  09:43 AM    <DIR>          .05/08/2012  09:43 AM    <DIR>          ..05/08/2012  09:46 AM    <DIR>          jdk1.7.0_0405/08/2012  09:19 AM    <DIR>          jre605/08/2012  09:44 AM    <DIR>          jre7               0 File(s)              0 bytes

and when I ran ant, it complained about not finding tools.jar under the jre7 subdirectory. It wasn't until I set "JAVA_HOME=C:\Program Files\Java\jdk1.7.0_04" that the error went away.

1. Install the Java SDK.

2. Add a System Environment Variable called JAVA_HOME with the value of JDK location.
   Go to Control Panel\System and Security\System. Advanced System Settings, Environment Variables, System Variables, New... Example:
   Variable Name:JAVA_HOME
   Variable Value: C:\Program Files\Java\jdk1.7.0_21

3. Close/reopen your CMD window so that the new variable takes effect before attempting to re-run the ant command.