by AverageJoe » Mon Jun 22, 2015 6:12 pm
Browse World of Warcraft Classic\WTF folder and open the Config.wtf file in notepad. Search for "gxresolution" (I think that's the property but I'm not 100% sure) and it should have a resolution next to it, e.g.: 800x600. Change it to be 1920x1080 and save then try logging in and see if it's any different.
I'm not sure how the resolution is formatted in the file (I'm on my work laptop at the moment), so when you enter 1920x1080, make sure to change it similarly to what it was before, like if it was 800x600 when it would be 1920x1080, or if it was 800 x 600, then it would be 1920 x 1080.