File extensions

Hi
I have a PSP with 4:00 M33 fimware. I downloaded the games Bus Bunny - Lost In Time & Bugs and Taz which seemed to arrive on my PC ok but in *.7z format. I decompressed this and got a *.img. What I need is a *.cso or a *.iso. Also I thought your games came in *.rar format.
cdlt

.img is just another image format, you'll need to convert it for the PSP yourself.

Trouble is I don't know how. I have spent ages just getting to this stage. When I signed up with RomUlation I thought that it would be easier than this. Again I thought the downloads were in .rar format and eventually in .iso's not in .img's.

Another small thing how can I change EBOOT.PBP to an .iso file?