google did not bring up anything coherent for a search on 'passport memory c4b'. What is it, what does it do, and what is it installed on?
What are the specs of your computer? high memory usage warnings are usially viruses trying to get you to click on something, so check your memory usage (task manager, memory) and see if you are really low on system memory, and what might be using it all before you trust such a message.