In preferences the "launch at startup" is checked and greyed out.
I want to uninstall Greenshot but it tells me it is on and therefore won't let me uninstall it.
Greenshot has overtaken my other program, Gadwin, and I want to revert to Gadwin but can't get rid of Greenshot.
I even tried a system restore to get rid of it, no luck.
This error is telling you that the Greenshot process is still running in the background:
You can either close Greenshot by right clicking on its icon in the system tray, then choosing Exit:
... or by ending its task from the Task Manager:
The application will then uninstall normally once its process is no longer running in the background:
Mr Ethernet's answer is correct. You need to exit Greenshot in order to uninstall it.
In response to 'In preferences the "launch at startup" is checked and greyed out.': This happens if you installed Greenshot with admin permissions, but run it as a "normal" user. Exiting Greenshot and re-starting it as administrator should enable the checkbox.
