Does anyone know of a tool that will enable me to batch convert the dimensions of my large edited portraits TGAs into the smaller counterpart portrait cards?

I can convert the TGAs to JPGs and then batch process the dimensions and then convert them back to TGAs, but this is no good as I lose the alpha layer - and even if I knew how to save/reapply the alpha (which I do not) it just takes too long and I might as well go and do it all manually.

So, a tool that batch converts TGA dimension sizes anyone?

I have PSP 7 and GIMP 2.2 but cannot seem to find it there, PSP seems to just have a batch file format feature.

Thx.