<p>I'm trying to parse an INI file using C++. Any tips on what is the best way to achieve this? Should I use the Windows API tools for INI file processing (with which I am totally unfamiliar), an open-source solution or attempt to parse it manually?</p>

I have never parsed ini files, so I can't be too specific on this issue.
But i have one advice:
Don't reinvent the wheel as long as an existing one meets your requirements
http://en.wikipedia.org/wiki/INI_file#Accessing_INI_files
http://sdl-cfg.sourceforge.net/
http://sourceforge.net/projects/libini/
http://www.codeproject.com/KB/files/config-file-parser.aspx
Good luck :)