Might be no help but...
I'm using a regular, US keyboard. If I switch keyboards from "English (United States)" to "United States-International" then I can type
'C (apostrophe followed by a capital C).
With the "United States-International" keyboard, some characters like apostrophe and double quote cause the next character to be modified with an acute accent or umlaut.
If you want, there are Windows XP keyboard editors that will let you remap keys. You could take your current mapping and re-map a combination to Ç.