
Gamemaster406, yes, you can. However, you will no longer have a clean copy of CFS3, in case you would like to install another CFS3-based theater, like PTO or MAW.
Here is a way to keep a clean copy after installation of Firepower:
1. Simply make a copy of your Combat Flight Simulator 3 main game folder. Just copy it into the same folder where your original resides: C:\Program Files\Microsoft Games. The copy should bear the name Copy of Combat Flight Simulator 3.
2. Install Firepower into the original. Do NOT start the sim yet.
3. Go into your CFS3 ETO Expansikon main game folder, and look for a file named MultiCFS3.exe. Then copy this MultiCFS3.exe file into your original Combat Flight Simulator main game folder where you just installed Firepower.
4. Now, while in the CFS3 main game folder with Firepower installed, run the MultiCFS3.exe. Simply use it to rename your original install to reflect Firepower. Again, do NOT start the sim yet.
5. Also, rename your original CFS3 main game folder to reflect that it now contains Firepower.
6. Go to your desktop, or whereever your CFS3 start icon is located. Make a new folder and copy the CFS3 icon that is there into this new folder. By all means, name this folder to reflect that it belongs to a Firepower install.
7. Now go into the folder that contains the new copy of the CFS3 start icon, right-click on the icon, and choose Properties.
Where it says Target, simply type this: "C:\Program Files\Microsoft Games\Combat Flight Simulator 3\cfs3.exe"
Be sure to include the quotaion marks, as I have just shown them above.
Also, where it says Start In, type this: "C:\Program Files\Microsoft Games\Combat Flight Simulator 3"
Again, show the quotation marks, too, as I have shown above.
8. Now then, go back to C:\Program Files\Microsoft Games. Look for the folder named Copy of Combat Flight Simulator 3. Rename it to read Combat Flight Simulator 3.
9. Now start the Firepower install with the newly-made icon in the new folder you made.
You should be good to go now, with your ETO install, your new Firepower install, and a clean copy of CFS3.
Hope this helps.:d