The first is very general, go to any window where you can access the C: drive. For example My Computer or Windows Explorer (To Access Windows Explorer either right click on the start button, and then click explore, or go to Accessories and click on Windows Explorer). Right click on the C: drive icon and click properties. In the Window that comes up you will see a pie chart which represents your hard drive. Above the pie chart is the Word Capacity, there is your answer.

Or you can also right click on any My Computer icon, and then click manage. This will bring up a window named Computer Management with a left pane and a right pane, in the left pane look for the words Disk Management, click on this and allow the program to call up the disk information in the right pane. Now when the read out changes in the right pane look at the bottom of the pane, for disk 0, the capacity will be there as well.

Hope this helps.