[how real is it to power an inverter of 1.5kva with a solar panel]

If you want to raise the voltage to 110V AC or worse to 230V AC, you will -for sure- be out of current(depending of the voltage output of your panel).
You have to connect many panels together to achieve your goal.
But it should not be a simple connection :-\

Kyriakos

[FM Radio]

Ok, you may use it as a simple analog radio receiver ;)

About the other matter, the "low-high pass", I can only guess for what you are talking about. I think you mean "tone control" which suppress or raise the low-high frequencies of the acoustic bandwidth.
Well this receiver doesn't have any of these 'whistles' because of it's simplicity. It is a mono (not stereo) FM receiver.

[FM Radio]

Hello EDY,
you are correct. IC3 and its complementary componets are a just a sound amplifier and can be ommited. You can put the sound signal (taken from potensiometer's P1 wiper) directly into your's soundcard AUDIO input so that you can have totally digital control over your radio receiver.
(You realise ofcourse that tuning isn't exactly 'digital' but looks like it :o) )

The DOS software I have, is very old technology :( and has several bugs. If you want to look for something else, search for any freeware Parallel Port access tool on Google. You should find something...

Kyriakos