make sure you have the latest video drivers loaded on your desktop pc. Next I would check the video settings. I saw a post for this somewhere on the EQ EMU forums I will try to locate and link to it. (try lowering your video settings if they are maxed out.
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Someone posted:
You might also want to try adding "WindowedMode=TRUE" to the [Defaults] header (the first section) of your eqclient.ini. That fixed it for me. If you're confused, just add "WindowedMode=TRUE" to all the sections of eqclient.ini.
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Here is a link that may help as well:
http://www.eqemulator.org/forums/search.php?searchid=976057