Removing a Sitecore instance is usually a pretty painless affair.  On a day-to-day basis you have a few options open to you. One of the easiest options is to just use Windows.  For every Sitecore instance you create, an entry will be made in the program files.  To remove an instance, go to Control Panel -> Programs & Features, and find your Sitecore instance entry, as seen below:


You can also uninstall a Sitecore instance through the installation executable:


My preference via the Sitecore Instance Manager:


When Things Go Wrong

As dev's we sometime do silly things, or, we just hit an issue where the installer fails... it happens.  Not being able to remove your Sitecore instance can be very annoying.  One big annoyance is that the instance name can't be re-used on that computer ever again. This also usually results in a Sitecore instance living forever in your installed programs.  

If you run into install issues for the same time a few times, say when you upgrade, the developer is required to come up with alternative instances replacement instance names. These names can result in a bit of a mess on the developers PC as you end up with 5 entries in Programs, 4 which don't work and 1 that does. Happily manually uninstalling Sitecore isn't too painful. Below will cover this process:

Step One - Clear IIS

Open IIS and delete the instance from IIS

Step Two - Delete Your Database

Open SQL Explorer, find the Sitecore instance databases and delete all of them

Step Three - Delete Files

Go to the instances root folder and delete all the files

Step Four - Remove Temp Data

When Sitecore installs, some data is copied to the user accounts local temp storage. These files can sometimes be referenced when you try to uninstall so it's a good idea to check they have been deleted and remove them In 'C:\Users{username}\AppData\Local\Temp\' then delete the instance folder

Step Five

Clear your registry. When Sitecore installs, it saves information about your instance in the Windows Registry.  If you open regedit.exe and navigate to the Sitecore area, which can be found: HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Sitecore CMS In here you will see an entry for each instance you have installed.  Make sure you don't have an entry for the problem instance.  If you do just delete it.


Step Six

Download CCleaner and use the program uninstall feature to delete the instance from Program Files.  CCleaner will remove the entry from your Program Files won't work in normal circumstances. This should now remove everything from your Program Files and you're good to go :)