First of all download patch from this link --https://hotfile.com/dl/152883824/3c04692/IdmPatch_keys.rar. Then unpack copy and paste patch in ur IDM installed folder. Open and apply patch then disconnect internet connection and enter registration key. After doing this idm will never ask u for serial key and fake key message will never b appear.. remember dont try to update idm.. - idm serial key new (these serial keys work 10 times) , means if serial key used by 10 users, i.e one key can register only 10 times on diffrent computer.
Another trick if u recieve fake serial key key message.. Disable your internet connection before entering the serial key, or else it wouldn't work!
Try anyone of these first: