You know how to use explore?
Fastest way to get to explore is to Right click the Start button and select Explore.
Then go to Program Files/Squaresoft (something or other)/FF7
(I don't remember the path)
Right click a program, such as FF7.exe, And then select properties.... and somewhere in that Box that pops up you should see a Tab about compatibility mode.
As for Dxdiag.....
Open up that "Run..." in your "Start" button... and just type, dxdiag. And then go to the Sound Tab....you'll see it.