HDD's are a dime a dozen nowadays (shortage due to floods not withstanding). So your best bet would be to get 2x 7,200RPM 1TB drives, and then you can either RAID0 them for speed (Striped) or you can RAID1 them (mirror) for redundancy. Then you can get a 120GB SSD as your OS and install hard drive. This means that you can set your machine up to run everything off the SSD (Windows 7 and the games you install) but save all your downloads, ISO files, music, movies and stuff to your 1TB drives. Which in turn means that whenever you fancy rebuilding your machine, (wiping everything and re-installing the US) you won't lose your music and movies and stuff. Fans are completely generic and will work with pretty much any motherboard, however it is worth checking if your case don't come with a couple already installed. RAM is available by the shedload from dabs.com, you need DDR3 ram and your machine is a desktop configuration. (tower is just the size of the case if it's not a server, it's a desktop.) ---built my own PC from the ground up.