Sigh, I hate those silly warnings, but oh well...
INCLUDES REGISTRY WORK!
Registry entry should be here: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\CDCE6956-DD16-4F82-ACA0-E4C7BAD6B26A_is1
You always can delete it and the entry will disappear in Uninstall Tool. As for leftovers, they are here:
-> HKEY_CURRENT_USER\Software\Larian Studios
-> HKEY_LOCAL_MACHINE\SOFTWARE\Larian Studios
Also, there could be sumtin from DTP, look for "dtp" or "dtpEntertainment" in those sections. That's all for the registry.
All old savegames/user options is in: c:\Users\%username%\AppData\Local\Divinity 2\
