Okay get your hands ob Smilla enlarger. as seen in the image.
Save TGA as BMP.
Set them all in one folder. :P
Set Smila Enlarger to 400% rescale.
Either use painted or Sharp.
Drag and drop all the bmp into the Jobs Tab... And presto it does them all for you. :P
The it is just a matter of scaling them back 50% with another drag and drop into the Jobs folder.
And presto you should have an obvious set of Icons that are 128^2....
This is just a theory. :P
Of course you could just 200% it and leave it there with sharp or painted.
Remembering when you get icons you are happy with they must be changed back to TGA and named appropriately. :)