So you're saying the hard drive in "My Computer" isn't showing up? Like the C: or D: or one of your drive partition isn't there anyone? Have you check Computer Management>Disk Management?
If you're typing and able to save and open and what not and all that good stuff, I'm pretty sure your local disk is there and in good health.
Try restarting your computer. Sometimes computers get confused and place icons in the wrong places and take a restart or two to get them thinking better again.