The .3dc files are color settings for another application - 3D color changer 3000. If you don't have that installed, then the color settings are not going to work - at least not those. It'll still use whatever system colors you have assigned when you select "apply colors to theme", but I don't know how good they'll look. =)

That app (freeware) is available here, among other places (as always, scan for viruses):

http://www.softlookup.com/display.asp?id=25953