are ISO same with CSO in terms of copy pasting on the ISO root of the mem stick? im still a newbie but i've tried the copy pasting of a CSO file which is really easy...so how will i transfer ISO files to the mem stick of the psp slim?thanks for the help

CSO are just compressed versions of the ISO. Both transfer the same and go into the same folder which is the ISO folder on your memory stick. As of right now there is not a way to play an ISO nor CSO on a PSP Slim. You must have a fat PSP with custom firmware to play either one. Hope this helps.

so what this means i cant play downloaded games on slim cuz i already played my nfs carbon on psp

You can play ISO/CSO on the slim, just get a custom firmware, for example 3.71 M33-3.

pretty much the same just dif sizes