Windows 7 - New hardware not working or reading properly, Help?

Okay so today i got a 2gb stick of what my boss told me was either ddr2 or ddr3 RAM, I installed it easily as it should be but when i look at how much memory i have it says 5.00GB (4.75 Usable) This should be 5.75 for both total and usable.. Also today i bought a 320GB Western Digital Caviar Blue HDD and i looked everywhere for installation software as i did not get a disk, Nor instructions on how to install it other than how to plug it all in.. It will not show up in (My Computer) but Disc manager confirms its there, and for some reason is using it for MBR Master boot record. Can someone help me fix these two problems? ANDD... After all this my Nvidia 8400 GS will not work.. When i plugged everything back in i started up computer and my monitor wouldnt get a signal from the computer. I put my VGA into my Nvidia 6100 Integrated on my motherboard and i have picture now.. Help?