The *right way* is using the SHGetFolderPath() function.
The minimum requirements are (from MSDN):
"Windows 95 with Internet Explorer 5.0, Windows 98 with Internet
Explorer 5.0, Windows 98 Second Edition (SE), Windows NT 4.0 with
Internet Explorer 5.0, Windows NT 4.0 with Service Pack 4 (SP4)"
And what you probably want is CSIDL_APPDATA (the application data
folder).
As you can see, every windows version since Win98 SE comes with it,
and every other that upgraded to IE 5.0 (and who didn't has the PC
infested with virus, anyway) also got it for free.
I would say it's old enough, don't you think? ;)
Regards,
~Nuno Lucas