Asus/Gigabyte/MSI motherboard with decent amount of SATA ports (at least 3), up to date chipset, and of course supporting your CPU choice;
CPU: AMD Phenom II or Athlon II quad core / Intel i5, i7 quad core
RAM: 4 to 6GB
Graphics: AMD/ATI HD5770 1GB or nVidia Geforce GTX260 896MB
HDD: any will do as long as it's SATAII and reasonably fast
DVD drive
ATX case
Corsair 450W or 650W PSU
Due to your lack of preferences basically any decent rig would fill your criteria. Please give more information. How about you look up some parts that you think are good, relay them back to us/me and we'll tell you if they're any good.
cheers