Added RAM to T6414 emachine and it will not turn on

I added 2x1GB sticks to T6414 emachine and I can't get it to boot. When I first added the sticks, I left the 2 stock(2x256MB) in the machine because I have 4 slots. I was getting a beep every 5 seconds on boot up. So, I had removed the 256 sticks and put the 1GB sticks in their place, same ploblem. Then, I returned the machine back to original figure(2x256MB in the same slots). Same problem, so I removed Bios battery for 15 seconds, no luck. One thing that was odd to me, is when I checked the RAM before the upgrade, the pc stated 384MB of RAM. Why not the full 512MB? I had Crucial scan my pc for memory upgrade to ensure the right RAM(PC3200 DDR 400MHz). Any help, thanks