Hint: I'm not convinced that which IDE you are using is relevant.
It may be, at least in regards to advice on ways to check how it is configured; it may be using a different search path than the one you think it is using, for example. In other words, it may matter iff you aren't sure what it is doing, and need help with the IDE itself (as opposed to the programming).
However, such a problem is something that should be addressed before you even consider OS dev. You might also find it better to try a message board specifically about C++ and/or the IDE you are using
(and by that I assume you mean the Orwell fork
; if you are using the older, unmaintained Bloodshed Dev-C++, then for Eris' sake, delete it right now
and get one that has been updated more recently than 2005). I have used Dev-C++ before, and a few others here may have as well, but I doubt there is anyone here who is an expert on it.EDIT
: OK, I can see from the screenshot that it is indeed the current version of Orwell Dev-C++. That's at least something. Unfortunately, checking the SF repo, it looks like that fork has stalled as well, with no updates since June 2015. Have you considered using something like Eclipse, Code::Blocks, or Geany, instead? For that matter, you might want to set aside the IDEs entirely and get your hands dirty with the command-line tools for a bit, if you haven't done that before, as it can really help you understand the things those tools are doing for you - automation is great, but to use it well you have to understand what is being automated.