This will work for all Office '07 Programs (PowerPoint, Excel etc.) but Word has been used as an example
1) Open your program, and click the office button (top left)
Click the 'Word Options' button (obviously differs between programs)
This dialogue box should pop up:
Be sure to check the circled box.
Now the Developer tab should be there along with all the others:
If not - try these steps again!
The Developer tab itself looks like this:
with options mainly for visual basic and macros, but a couple of other settings to be found too - for example, another method of showing the file path in the header/footer (as explained here)
If you have any further issues, please do not hesitate to post here, and somebody will reply to you in no time =]