My cygwin installation contains the following ruby binaries, how can I uninstall these binaries since I would like to use ruby 192 on my windows vista machine
To uninstall any package on Cygwin, run setup.exe (which you should already have), select "ruby" under "interpreters", click the round arrow icon until it says "Uninstall", then continue. This will remove the executables and libraries and take care of any dependencies. You could remove the files directly, but that might leave the system in an inconsistent state, and you might miss something.
Cygwin doesn't seem to have Ruby 1.9.2 yet, unfortunately. How do you intend to install it? If you're going to install a pure Windows (non-Cygwin) version of ruby, you may not need to uninstall the Cygwin version. For example, I have both Cygwin Perl and ActiveState Perl on my Windows 7 system; I use one from the Cygwin environment, the other from the Windows environment.
Or I suppose you could build ruby 1.9.2 from source under Cygwin; in that case, yes, you would want to uninstall the Cygwin ruby installation first.
http://www.ruby-lang.org/en/downloads/ has more information about ways to install ruby (but nothing specific about Cygwin).
UPDATE : As I recall, there are now two separate installers for Cygwin, one for a 32-bit installation and one for a 64-bit installation. The cygwin.com web site seems to be down at the moment, so I can't verify the names.