GP3 CD Trouble

This might be interesting to you, if you cannot get past the "insert CD screen" in GP3-2000. All of a sudden, this beautiful game asked for a CD in the CD-Rom drive, which it never did before (have been playing it for years). For sure I use the decrypted exe file, which has always worked. So what has changed on my computer lately? Last week, I removed the CD-Rom drive to use the data cable for another hard drive. This was the problem, as there was no CD-Rom drive present, it prevented GP3 from starting. After reinserting one, the game worked perfectly.