Head to http://www.crucial.com and see what is offered for your machine.
HOWEVER I would consider what OS this machine is running. If 32BIT, no gain.
My sister has a Dell 5455 Inspiron Pentium with Duo Core CPU. It came with 4 gb memory. Can this computer be upgraded to 8gb?
I recently upgraded my Dell I5 to 16gb so now have four 2gb memory sticks and I would like to put them in her computer if it will allow me to upgrade to that.