Access is denied for "bootstrap" command

Hi,

I have downloaded BGL (Boost Graph Library) to work with my Visual Studio C++... It works fine with BGL files that do not need to be built... Now, some BGL files needs to be built... I have to go to the BGL directory from the command prompt and enter the "bootstrap" command... It works on some machines... But on my machine it gives me:

"Building Boost.Build engine

Access is denied.

Failed to build Boost.Build engine.

Please consult bootstrap.log for further diagnostics"

My machine is an HP Workstation and I'm using Windows 7 professional edition... Why do you think I'm getting Access is denied?