Please help, I need to install XP on a Dimension E521 that originaly came with Vista, need to know if its possible to use a XP cd that originally came with Dimension C521 and is a Reinstallation DVD of Windows XP Media Center Version 2005, don't know much about computers and not sure if is legal since I been reading a lot of posted messeges. Unless I have to buy a brand new XP cd to install it. I have all the cds that came with both computers which includes the drivers/etc. Please help!!