Login Dialog is off Screen

[corshmock]

Hi Folks,

Newbie here. When I boot up my Debian machine, the login dialog is over to the left hand side of the screen with only half of it showing. I've taken a photo of it but can't see any way to attach it.

I've tried right clicking on the desktop and changing settings to no avail. I am only using one screen, which is sitting on the closed lid of my laptop.

Hopefully someone will understand what I mean and be able to offer me some help here.

Apologies if I'm in the wrong section.

Thanks very much

Kind regards

Corshmock.