ya_know raises some valid points (and not just regarding this particular topic)
One of the most frustrating aspects of poorly-written applications is that they leave behind a lot of "junk"; both in the system registry and also on your drive (as file system objects).
One of the best ways to get around this problem is to get in the habit of seeing exactly what an installation does to affect the environment of your operating system. A good way to do this is to download and install a program called InstallWatch. This app is available as a free download, and makes a useful addition to your arsenal of utilities. You can get it at:
http://www.epsilonsquared.com/
Upon installation, this program will take a snapshot of your hard drive, and then create a small database that uses a reverse delta history of changes made to your drive, thus eliminating the guesswork involved with trying to get rid of "lamerware" on your machine.
There is another app on this site called InstallRite that supplements InstallWatch by allowing you to build your own installer programs without having to spend a bunch of cash on the fancier packages (like Wise or InstallShield) -or- go barking mad trying to write installation packages using Microsoft's MSI technology. This comes in rather handy when trying to do things that are not normally possible, like installing IE6 or the .NET framework on a Windows 95 machine.
Granted, all of this information is moot after-the-fact, but if you get acclimated with these tools & become disciplined in using them before installing new software, you will eliminate most of the headaches involved with hunting for CLSIDs & GUIDs in the registry. This should make your time spend in front of your computer much less exasperating, and also serve to facilitate the allocation of more free time to dedicate to the consumption of alcohol & the carnal exploitation of consenting females.
Hope this information helps!
-mike
