I still can't remember what it was but I just realised it can be done with good old WinRAR. Put all the 7z files into a folder, select them all and extract them. Now move all the 7z files out of the way somewhere. Open WinRAR and navigate to the roms folder. Highlight all the files and right-click, then 'Add to Archive'. Change 'Archive Format' to zip in the General tab. Then click the 'File' tab and down near the bottom tick the 'Put each file to separate archive' box. It'll take some time obviously, depending on how many roms you are unpacking/packing but at least it's all automated! Edit for minor details good tips. thats what I'll do. damn we are talking about 2 gigs of roms, 3000 or so files.