If you have a T&L capable video card with at least 32 MB of video RAM then you need at least:
# 600 MHz P3 processor or better
# 256 MB RAM if Windows XP, Windows ME, Windows 98 or Windows 2000
# At least 3.5 GB of hard drive space
If you have a non-T&L capable video card (such as Intel Extreme Graphics or Radeon 7xxx Series) then you need at least:
# 2.0 GHz processor or better
# 256 MB RAM if Windows XP, Windows ME, Windows 98, or Windows 2000
# At least 3.5 GB of hard drive space
Supported video cards (and the more video memory the better):
# ATI RadeonTM series (7000 or better)
# 7000, 7200, 7500 (requires 2.0 GHz processor)
# 8500, All-In-Wonder 8500
# 9000, 9200, 9500, 9600, 9700, 9800
# Nvidia® QuadroTM series
# Quadro, Quadro2, Quadro4
# Nvidia® Geforce series (GeForce2 and better)
# GeForce2
# GeForce3, 3 Ti
# GeForce4, 4Ti, MX 420, 440
# GeForce FX 5200, 5600, 5700, 5800, 5900, 5950
# GeForce 6800