Go into the OOTP5 folder and open the "game config" file, toggle the 3d setting, close those things and try the game again.
If that doesn't solve it, go to start then run and type dxdiag and hit enter. The direct X utility will open and it will let you know what version of direct X you are have installed. If it is less than v9 go to
http://www.microsoft.com download and install v9, reboot your computer and then try the game again.
Other possible solutions:
-Update your video drivers.
-Change desktop color depth.
Please let me know if none of these help.