What you want is Matryx's mod launcher. You run it from windows and it lets you select which mod you want to use. It also displays a little information about som of them. Then you just click "play SEIV" and it will run the game with your chosen mod. It has other features too=-)
Put a few searches into this forum to find the mod launcher. Assuming your mods are installed correctly (and that they're fairly modern ones which don't overwrite the original files), installing the launcher is just a matter of unzipping it to your SE4 directory and creating an icon for it.
The alternative is changing the path.txt file every time you want to change mod. Not fun.
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SE4 Code:
L GdY $ Fr- C- Sd T!+ Sf-- Tcp-- A% M>M+ MpD! RV Pw Fq+ Nd- Rp+ G-
/SE4 Code
Work out your code at
http://www.sandman43.fsnet.co.uk/se4main.htm