Can't download minecraft forge b/c it tells me that I need to play minecraft v1.7.2?

In your Minecraft Client, create a new profile. In the versions option (around 3/4th the way down) it'll be set to either "Current Version" or "Version 1.7.9.". In this you click "Version 1.7.2." and click play.

After you've entered the game, close and install Forge in the 1.7.2 folder in in the "Versions" folder in the ".minecraft" folder. After that's done, check to see if it installed correctly.

Thanks I got it.

You need to go to profiles and click the version thing and select the 1.7.9 play it and close the game down then install forge

Change your MC version to 1.7.2

Try google it also