The cheapest graphics card you can play it on is an NVIDIA GeForce 6100. PCMark 8 system requirements state that you will need at least 2 GB of RAM. An Intel Core 2 Duo U7600 CPU is required at a minimum to run PCMark 8. You will need at least 30 GB of free disk space to install PCMark 8.
PCMark 8 will run on PC system with Windows 7 and upwards.