Convert gg to psd Online: gg2psd

You can use Tom's Editor to easily convert images from
Koala Painter 2, packed .GG to Adobe Photoshop .PSD.
Tom's Editor is a free, online image manipulation and converter program.

Go to Tom's Editor

GG

Koala Painter is a Commodore 64 program do edit images. GG images are packed using RLE compression.

PSD

PSD is in internal image format of Adobe Photoshop. It can store all the features offered by Photoshop, like layers and paths. Images can be compressed or not.