It's a big tower with a normal sized ATX mobo. My older PC was 6-7 years old already, and annoyed me lately whilst multitasking, and also streaming HD material to the PS3.

I also only had 760GB of HDD space (IDE disks), and had to backup everything on slow external USB drives. Now with 6TB (SATA/300 --- reading at 135MB/s) I can do that internal, and a lot faster.