These are the System requirements that I have read.
Once again,please do not hold my feet to the fire here.

Windows XP or Vista
700 MHz Pentium class or compatible (1GHz or faster recommended)
512 MB system RAM (1 GB or more recommended)
OpenGL enabled graphics card or chipset recommended • (recent NVIDIA GeForce and ATI Radeon preferred)
24-bit color display, 1024 x 768 resolution
2 GB free hard disk space (4 GB recommended)

Macintosh
Mac OS X 10.4 or 10.5
700 MHz G4 processor (Intel Core Duo or 1GHz G4 or faster • recommended)
512 MB system RAM (1 GB or more recommended)
OpenGL enabled graphics card or chipset recommended • (recent NVIDIA GeForce and ATI Radeon preferred)
24-bit color display, 1024 x 768 resolution
2 GB free hard disk space (4 GB recommended)

"That government is best which governs the least, because its people discipline themselves."
Thomas Jefferson