1. n. A dedicated area (usually enclosed by a fence) of a park where cats may be execised untethered, which would otherwise be in violation of local leash laws (N.B. cats do not run for exercise);
2. n. A good idea which is bad ipso facto (etym. New Yorker cartoon from 26-Jan-2009 issue).
Windows Vista was a total cat run; upgrade to 7, dude.