I've -finally- successfully installed G.E.C.K. along with the steam version of Fallout 3. The initial set up works well and I can import the .esm master file from File > Data > Fallout3.esm but following the tutrorial on the G.E.C.K. website it recommends I now save, this is where I encounter problems. I try to save but I only get a 'Invalid Directory' warning message. I've tried saving it in the source folder where I have the G.E.C.K. programme installed as well as where Fallout 3 is installed, I've even tried saving it in C:// > Programme Files (86x) > Bethesda Softworks > Fallout 3 (sometimes > Data) but still nothing.

Any one have any advice on how to solve this?

MG__

The GECK should be installed in your root Fallout 3 folder.

You would then save in the same folder path, but in the 'Data' folder.

If you don't have it setup like above, you will get an invalid directory warning.