The JackCompiler runs from the command line (cmd.exe), not from a desktop shortcut or clicking on JackCompiler.bat in Explorer.
You need to add your nand2tetris\tools directory to the PATH environment variable so that Windows can find the batch file.
On Windows 7, right-click "Computer" icon and select Properties. Go to the "Advanced tab" and click "Environment Variables..."
Scroll down in the System variables list and select "Path" and click the "Edit..." button and add  your nand2tetris\tools directory, followed by a ';', to the beginning of the path. Close all the dialogs and start a new Cmd window. Type "path" and you should see your directory
C:\Users\marka>path
PATH=d:\TECS\tools;c:\usr\binw;c:\python3.4;c:\python2.7; ... etc.
C:\Users\marka>
Now you should be able to use JackCompiler from the command line without needing to type the full path name
C:\Users\marka>d:
D:\>cd tecs\projects\09\Reflect
D:\TECS\projects\09\Reflect>dir *.vm
 Volume in drive D is SHAREDDATA
 Volume Serial Number is CCFB-1BE4
 Directory of D:\TECS\projects\09\Reflect
File Not Found
D:\TECS\projects\09\Reflect>JackCompiler
Compiling "D:\TECS\projects\09\Reflect"
D:\TECS\projects\09\Reflect>dir *.vm
 Volume in drive D is SHAREDDATA
 Volume Serial Number is CCFB-1BE4
 Directory of D:\TECS\projects\09\Reflect
04/10/2015  07:18 PM             5,197 Ball.vm
04/10/2015  07:18 PM             6,481 Game.vm
04/10/2015  07:18 PM             6,975 Main.vm
04/10/2015  07:18 PM             3,687 Mirrors.vm
04/10/2015  07:18 PM               864 Random.vm
04/10/2015  07:18 PM             2,659 Target.vm
               6 File(s)         25,863 bytes
               0 Dir(s)  12,094,406,656 bytes free
D:\TECS\projects\09\Reflect>JackCompiler /?
Usage:
    JackCompiler              Compiles all .jack files in the current
                              working directory.
    JackCompiler DIRECTORY    Compiles all .jack files in DIRECTORY.
    JackCompiler FILE.jack    Compiles FILE.jack to FILE.vm.
D:\TECS>
--Mark