Minimum:
AMD K6-3 400MHz, Pentium II or Celeron-A 300MHz
64MB RAM
Fully OpenGL compliant 3D accelerator
100% Windows compatible sound card
Windows 95 OSR2, Windows 98, Windows 98SE, Windows ME, Windows NT 4.0 (with Service Pack 5), Windows 2000 or WindowsXP operating system
150MB free hard disk space

Recommended:
AMD Athlon 650MHz or Pentium III 650MHz range processor
192MB RAM
3rd generation full OpenGL compliant 3D accelerator with 32MB RAM
Creative Labs SoundBlaster Live
450MB free hard disk space

For full experience:
AMD Athlon 1GHz or Pentium III 1GHz range processor
256MB RAM
4th generation full OpenGL compliant 3D accelerator with 64MB RAM