Not enough memory to perform operation

wenever i try to transfer songs into mi N72 from mi friend's cel..it says not enough memory. despite the fact that i hav a 512 MB memory card installed. i dont have any songs in my phone as i have formatted mi phn and memory card, as i had virus in my phone. but now it seems that the phone does not detect the memory card. becase everytime i try to copy songs it comes in my phn memory which is less to perform any function. i ahve even tried to change the memomy for the msgs bt it seems like it never detects the memory card. and at last how can i forget.....it hangs like Hell!!!!!! :(