Minimum requirements:
450 MHz Intel/AMD Processor (or compatible)
96 MB RAM
16 MB Direct3D Compatible Graphics Card

Maximum... err, recommended requirements:
700 MHz Intel/AMD Processor (or compatible)
128 MB RAM
32 MB Direct3D Compatible Graphics Card

"Stephen Wolfram is the creator of Mathematica and is widely regarded as the most important innovator in scientific and technical computing today." - Stephen Wolfram