That's because both the regular game and TSF are merged into one game in your case. Well, not exactly, the TSF just uses its own exe file (which has overwritten the regular JJ2 one), but it can detect any episode and levels made with any lower version.

In the first releases TSF and and the regular JJ2 came on two seperate disks, and each has its own exe file, which means they're two seperate games. Some of later rereleases (like the Polish one) had the entire package merged onto one disk.

- JelZe GoldRabbit =:3