It helps to post your graphics card type.
Belongs in games?Also, I didnt know Terraria was available off of Steam.
Then you can't run it.If you're really wanting to run it, then download Swiftshader. Drag d339.dll and SwiftShader.ini into C:\Windows\Microsoft .Net\assembly\GAC_32\Microsoft.Xna.Framework.Graphics\(whole bunch of numbers) It will be VERY slow though.
I'm uploading the .rar.Just extract the .rar file into C:\WINDOWSAfter that, try playing.
Ummm where the file