It depends on how it was installed, if it's an RPM then (as root) do rpm --erase {program name}. If it was installed from source then (as root) cd to where the source code is located (i.e., /usr/local/someprogram) and type "make uninstall". This may not work in all cases, but should work in most. If it doesn't work then you'll have to look in the Makefile for the program to see what it installed and where and manually delete the files.
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