Did it look like this?
Because Project M should not interfere with regular Brawl.
If you did get that particular message, that means that your disc reader is broken, and you need to get a new one.(Or a new Wii.)
Post Merge: August 07, 2014, 08:37:31 PM
If you're asking where the Brawl files are that you put on to "hack" Super Smash Bros., that would most likely be in either "SD Root->private->wii->app->RSBE->pf" or "SD Root->ssbb->projectm"; it could be a different directory though; in any case, all hacks are put in the same main folder, so if you find a folder called "fighter" or "module" or anything, that means that the folder containing those folders is the root folder for mods.