GnatBench (from GPL edition)

I've just installed the GPL version of GNAT, with Gnatbench 2.0.1 into
Eclipse. I created a new Ada project, a "Hello World" one, and set the
toolchain to gnatmake. When I try to build it I get:

"Could not execute command 'make
GPRPATH="C:\EclipseWorkspace\AdaStartProj\AdaStartProj.gpr" build"

Does anyone know why that is?

Why is it not trying to run gnatmake directly?

Does it make a difference that I'm using Eclipse Europa (3.3.1.1) and
CDT 4.0.2?

Thanks
John