No, rikaichan works only within Firefox and Thunderbird. As far as I know, there aren't any programs for Windows that will do the same thing as rikaichan system-wide.
Yeah, I wish there was something like that out there, too. As complex as rikaichan had to be to write, a program to do the same thing for the entire OS would be a monumental project, I imagine. There is a program that does the same thing in Mac OS X (though I've personally never gotten it to work...) that makes use of Mac OS X's accessibility features.
Jason wrote:It seems that Wakan has popup support for more programs, though it's listed as experimental.
Great site BUT it's not compartible with Windows Vista so I'll have to keep waiting until everyone (all softwares companies) finally update their programs.
I know this is an old question, but I wanted to say there is now also something called RikaiKun. It works like RikaiChan, but in Chrome instead of FireFox.