|The hard drive needs to be partitioned in order for it to appear in 'My Computer'.|
Right click 'My Computer' and click manage, then go Storage -> Disk management. It will load for a bit and then your drives will appear. Partitioned drives will have a blue bar at the top and unpartitioned will appear with black bars.
Right click the unallocated space and there should be an option to partition the space, all the default options in the prompts should be fine. It will ask if you also want to format the drive, click yes and once its finished your good to go! It should appear in 'My Computer' now.
4GB DDR2 800