Well there is this link which covers most installation troubleshooting problems:

http://forums.fsmod.com/viewtopic.php?id=9938

Pay particular attention to this bit:

UNABLE TO RUN FIRST STRIKE WITH DIGITAL COPY OF BF2142

Those who have a digital copy of BF2142 from the EA Store may have problems running First Strike, it may even ask you for the BF2142 disk. In order to get around this, you need to navigate to your BF2142 directory, usually this is program files/electronic arts/battlefield 2142. In this folder you need to find two items, BF2142.exe and FirstStrike.exe. Copy your BF2142.exe somewhere and then rename it to exactly match the FirstStrike.exe. Delete FirstStrike.exe from your BF2142 directory, then place your newly named .exe in the folder.

Tends to be the problem that gets most people, since BF2142 1.51 there have been a few compatibility issues, various different versions of the BF2142 exe seems to be the main problem, for some it works fine, for others they need to do this exe duplicating trick.