I had to wipe an instance of Sitecore today and start fresh. I deleted the instance using the installer, made sure to delete the App Pool and website in IIS. I removed any leftover files in c:\inetput\wwwroot and then when into SQL Management studio and deleted all of the databases it used. I then went to create a fresh instance using the same instance name and ran into this lovely error:
The Name You Entered Is Not Unique
Hmmm… What did I miss?
A quick Google and I found the answer, I just had to go into the registry and clean up a few things. I deleted everything under “HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Sitecore CMS” and then restarted the installer. After that it let me name the instance what I had previously used and I was able to continue installing with no issues!