Ok, I'm new here so, I didn't know where this thread should go.

Anyway, I have a PNG file that I want to use as a spray but I can't change it to a jpg without losing transparency and messing it up. How can I convert a PNG to a VTF file so I can use it?

What you can try is to convert it to .tga first, and then to .vtf using Vtex which is included in the Source SDK.

I am not sure if this helps you, but I think it can be worth trying.

If you need help converting it, then use: http://media-convert.com/

Photoshop always helps me. If you have it, you can convert anything to anything else in there.