Changed it to RGB, resized to 512x512 and added an alpha chanel.
I'm glad you're up-and-running
Edit: for future. With Gimp I resized the image Munk uploaded to 512x512* then created a new image set to 512x512, and in the advanced setting of creating a new image set "color space" to RGB and set the "fill with" to transparency. Copied, pasted and exported to .tga using the default settings.
* (I have a memory of reading somewhere that 512 was the laregest wow would except but that may have changed)