Note that the editor in the Keil <b>free</b> evaluation <b>is</b> limited in file size - 16K
http://www.keil.com/demo/limits.htm

I agree with Erik: your editor is your main tool - you need to invest in a good one if you're going to do this seriously.
I also agree with Erik that CodeWright is a <b>good</b> editor
http://www.starbase.com

I got mine from Grey Matter:
http://www.greymatter.co.uk

None of the IDE editors I've tried (MSVC, Borland, Keil) comes anywhere near CodeWright; after all, they're <b>compiler</b> vendors, and their expertise lies in compilers.
It'd be silly of them to put all the effort into creating what's already available in the likes of CodeWright!