I retired a couple months ago and had this old Dell Dimensions E510 that needed a new hard drive so I figured since I had time I would give it a try. When I open the case, I had 2 hard drives. They are Seagate Barracuda St3160812AS 160Gb. I ordered 2 Seagate Barracuda ST3250318AS 250Gb to get more hard drive space. If I understand this right when I install the new HD's I will loose the Operating System, which was Windows XP Media Center Edition 2005. I don't have any discs for this system. So I don't know if I have a 32 Bit or a 64 Bit system. I can't get it from the computer cause I can't get it to turn on because of the read disc error. I need to buy a new OS, can I update to windows 7 ? How can I know what to buy a 32 bit or 64 bit ? When I get the new Hard drives do I just install them ? I realize these questions are probably very very basic to you guys but if someone wants to take me under their wing and walk me thru this I would appreciate all the help I could get. Thanks Guys