What was the reason to install 4.0.0 on your F100 in the first time? 2.1.1 or maybe any 3
are way more advisable. The 4x series are intended for the F200, since the F100 versions just cut down functionality without any real advantage (read
these comments and add no USB-net support)
Anyway, there is
a 4.0.2 version of the firmware, but it is not clear if
updating is dangerous for "old" machines.
I installed 4.0.0 for SDHC support. Also that 4.0.2 you linked me to is for F200, I have a F100. And the dangerous updating is actually downgrading on the "new" F200b's. There is no problem downgrading with the F100's.
What I originally asked was how can I install 4.1.0 for F100 if it requires 4.0.2, but there is no 4.0.2 for F100.