I am not a big fan of storing CLIENT variables in the registry (I thought doing so was a hack when we first introduced CLIENT variables close to a decade ago, and still think that using the registry as a data store was a mistake). Actually, I am not a big fan of CLIENT variables altogether.
But having said that, a user contacted me with a problem. One of his servers contained so much CLIENT data that the registry had grown to several gig and Windows boot time was taking 50 minutes or so, and he wanted to know how to clear that data. Those numbers seem incredibly high, worryingly so, and I suspect that it’s not just all ColdFusion CLIENT storage. Nevertheless, I sent him this link to a ColdFusion script that we posted (back in 2005) that does exactly that, it purges registry keys (and can also list and create them for testing).