Dell Precision T5500 ram upgrade

Hi.

I have a Dell Precision T5500 currently with 15GB of RAM(4GB,4GB,4GB,1GB,1GB,1GB). I am wondering if I can replace 3x1GB sticks with one single 4gb so in the end it will be (4GB,4GB,4GB,4GB,Blank, Blank).

Will the workstation throw any errors if I do it?

Thanks