I have a Dell Dimension 4600 desktop in which I have 1 Gig of RAM. Lately I have decided to add another Gig of RAM. I opened the case and found that instead of placing a one Gig RAM Card, Dell had placed two 512 meg RAM cards. They are in the #1 and #3 slots. I have a one Gig RAM card from another machine that I would like to place into the first machine. Can I do this safely and, if so, which slot should it be placed into? Thanks