I am running Solaris Express 11 under Hyper-V and my monitor is "unknown" as such the maximum resolution is 1152 x 864. How can I manually tell Solaris that I want to use a higher resolution? Which files do I need to modify?
By default Solaris detects and then automatically uses whatever it thinks is best. If you disagree you need to create a /etc/x11/xorg.conf file and fill in whatever parameters you think are better. Any parameters not hard-coded will default back to the auto-detected settings.