RAM upgrade


I had an emachine running vista home that died on me so I gutted it for parts, drives and memory. I recently had a dell dimension 2400 given to me that I am using now but it runs very slow. I know by doing a system scan of the memory that it has 2 x 512mb of memory in it now. I pulled 3 samsung 1GB 1Rx8 PC2-6400u-666-12-ZZ out of the emachine can I use this memory in the Dell to increase performance?