yep im using it inside of the megabuild in the bin folder
I see, the only issue I'm seeing is that you have spaces in the directory path:
Change your "half life 2 beta" folder to be all one word or use underscores in place of the spaces.
Ie; halflife2beta or half_life_2_beta
Edit: and don't forget to update your hammer config to the new names.
Hopefully this fixes it.