Photoshop CS4 Keys not functioning

Well i recently downloaded a keygen, at first when i enter the code in this screen;

a green check mark appears at the end, saying the code worked…
but when i close photoshop and opening it for the second time this message appears, stating the code is invalid;
any help would be greatly appreciated.
Answer #1
is the key gen a multi product one if so are you sellecting the correct prog when generating the serial