Geany works great in Linux, I see that it's cross platform, so I guess you can also get it to work in Windows. But note that due to Windows not having the same compiler tools as Linux available by default, it might be handier in Windows to have something that comes with its own compiler like Dev-C++
Except it has this ability to leave trailing whitespace on the end of lines, can't do buffer local settings (i.e. can't set different a different value for tabstops depending on the file), and the last time I saw someone use it he would tap the space bar several times to indent because Geany's tabs to space conversion was broken and I don't even think it's configurable via some sort of script language. I don't really understand why people don't use one of the more established editors like emacs or vim. If you learn how to use one of those well then you're not going to regret it, but with something like Geany you'll eventually run into problems that these serious editors would already have encountered and solved.
Remember -- only 10% of anything can be in the top 10%.