First, make sure you have the FS2004 No-CD Patch file downloaded to your desktop.
Before using the patch, make sure you have already installed Flight Simulator 2004 (FS2004) on your computer using the original CDs or installation files.
Locate the installed FS2004 folder on your computer. By default, it is usually found in "C:\Program Files\Microsoft Games\Flight Simulator 9".
Take a backup copy of the "fs9.exe" file located in the FS2004 folder. This is an essential step in case something goes wrong during the patching process.
Now, open the downloaded No-CD Patch file on your desktop. It may be in a compressed format like ZIP or RAR, so you'll need to extract the contents first.
Dave The Diver