As Ethel says, you need to give more info. There are resources other than memory that can be too low. For example under versions of Windows before XP, the graphical resources were very limited, so that a couple of programs that used a lot of windows, scrollboxes etc., could eat up graphical resources, even though they might not require much memory.
Also what do you mean by 77% memory? Many people confuse memory (RAM) and hard disk space.