Memory upgrade

HI, I just bought a emachine. T5086 runs well I'm happy with it..it can just use a bit more ram.. it came with 1 gig...split into two 512 sticks. and all the computer has is two slots. So I bought a 2 gig stick. DDR2 ram by the way. anyhow the specs say that the memory capacity is 2 gigs with is what I have in it now. My question is. If i put another stick in that open slot. like one of the left over 512's or buy another 1 or 2 gig sticks to put in will that harm my computer? Did anyone ever try to exceed a PC's memory capacity?

Just wondering.
thanks
Pat.