[Dubya]

You could've done this:

pawn Code:

new checkname[128];
new playerName[MAX_PLAYER_NAME];
GetPlayerName(playerid, playerName, sizeof(playerName));
format(checkname, 128, "Users/%s.ini", playerName);
if(!fexists(checkname)) {
    // Player has not register.... Code Here.
} else {
    // Player has already register.. Code here.