photoshop question

TrueToMe

OK, I stumble upon this obstacle with .TGA file while modifying my crossfire marks.These marks are coming up with "WHITE" border background when I play the game even thought I "supposedly" save them with transparent background. I did a little research and found out that .TGA file need Alpha channels to be transparent but I'm using a fairly new Photoshop (PHOTOSHOP ELEMENT 7)there seems to be no tutorial that I could relate to. I hope someone who successfully create their marks with transparent background could help me or provide tips on how to solve this problem. Thanks, Justin