Did you download the BlackBerry JDE 4.0? I'm assuming you did not.
https://www.blackberry.com/Downloads...359F4AE7BD7BA1
Once installed, you can actually add the path to your path variable in Windows for ease of use. Click on Start then Run and type in sysdm.cpl and click OK. Click on the Advanced tab, then click on Environment Variables. At the bottom, select Path and click on Edit. Push the End key (takes you to the end) and add a semi-colon (;) and then C:\Program Files\Research In Motion\BlackBerry JDE 4.0\bin\ - cick OK and OK again and OK once more. Now you can just open a command prompt and type in rapc.exe from anywhere.