It will work, but you'd do far better to buy a WD Blue for the OS of a gaming computer - or better still, an SSD. Buying a WD Purple for your OS drive would be a bit daft, to be honest....
The bad thing about these for your only disk is they are not 7200 constant RPM disks. They are optimized for sequential streaming. They will work as your primary hard drive but they will be slower than a WD Black. If you were combining one of these with an 250GB SSD then you would be much happier.
It will work, but you'd do far better to buy a WD Blue for the OS of a gaming computer - or better still, an SSD. Buying a WD Purple for your OS drive would be a bit daft, to be honest....