Most software originating from Linux stores its configuration and data in a directory, which is not removed when the software is uninstalled (there is no registry like in Windows). Darktable is the same in this regard. Reinstalling darktable rarely helps (only if the software itself gets damaged, e.g. due to a hard disk failure).
As @MStraeten said, this directory is C:\Users<username>\AppData\Local\darktable; if you rename that directory (e.g. to darktable.backup), it will be re-created with default settings.
The log he mentioned, C:\Users<username>\AppData\Local\Microsoft\Windows\INetCache\darktable\darktable-log.txt, is in a hidden directory; either paste C:\Users\<username>\AppData\Local\Microsoft\Windows\INetCache\darktable directly into your Explorer (replacing <username> with your user name), or configure your Explorer to show hidden files (View hidden files and folders in Windows - Microsoft Support).
That log file can be opened in e.g. Notepad, and may contain details about your issue.