1.4? 1.5? Did you mean 1.94 and 1.95? The latest version of SE4 is 1.95, available on the main SE sites: Malfador.com, SEnet, spaceempires5.com, etc.
You can check the version of your SE4 install by opening the History.txt file in your SE4 folder. The latest version in this change log is the version of the game you have.
If you bought SEIV Deluxe, it will already be at 1.93 or 1.94, and you will not need the gigantic 1.94 patch. You just need to apply the 1.95 patch:
Patch 1.95
If, on the other hand, you have SE4 classic (1.02 was the release version, IIRC), or SE4 Gold (1.60), you will need to first apply patch 1.94, which brings those up to spec with the new MP3 based music system introduced in Deluxe:
Patch 1.94
Once you have such an installation patched to 1.94, you can apply the 1.95 patch from above.