Download this "fix", follow the directions in the "readme file" and you can set any resolution your video card can handle in the "d3d9.cfg" file settng.
http://files.filefront.com/SH3+XPSP2.../fileinfo.html
This is a missing part of the "readme file" incase you have any questions:
This DLL attempts to override the screen resolution set by a Direct3D 9 program. To install, extract this archive to the directory the program is installed to. Do NOT install the DLL into any system directories. Edit the cfg file for resolution and other settings.