We have a Dell Optiplex 755 which is freezing at POST and displaying what appears to be a hexadecimal string in the top-left corner of the screen, like so:

Any ideas on what is causing this?
We have a Dell Optiplex 755 which is freezing at POST and displaying what appears to be a hexadecimal string in the top-left corner of the screen, like so:

Any ideas on what is causing this?