At this moment my kmeleon 1.5.1 uses 47 MB of RAM.

OK, the problem is that if I close it with the laucher in execution (Fast mode), the instance of kmeleon shown in the task manager keeps using all 47 MB of RAM. If I instead of closing the browser minimize it, the memory use is reduced to 16 MB.

I know this last thing is due to the windows OS, but I'd expect that when I
close the browser loader.exe kept the reserved memory at a minimum, at less
at the level obtainable minimizing the window.

Please let me know if there is a solution.

It's possible that Loader need update for work fine with 1.5.X versions.

K-Meleon in Spanish

There is no solution? It is planned an update for loader.exe?

Minimizing doesn't free memory, it only move unused part to the swap. This will always happen when windows will need memory, so this is irrelevant.