The Blender Foundation recommends the following minimum requirements:
Three-button mouse
Open GL Graphics Card with 16 MB RAM
300 MHz CPU
128 MB RAM
1024 x 768 pixels display with 16-bit color
20 MB free hard disk space
However, if you really want to get maximum performance, there is a more powerful configuration:
Three-button mouse
Open GL Graphics Card with 128 or 256 MB RAM
2 GHz dual core CPU
2 GB RAM
1920 x 1200 pixels display with 24-bit color
There isn't much to say about the software, only that you can run Blender on almost any operating system available. The following is the list of systems that support Blender: