How Do I Change My Only Hard Drive From H: To C:.

Yes, you can map the drive to C rather than H.  To change a drive letter Using the Windows interface:

Open Computer Management (Local). (To open Computer Management, click Start, point to Settings, and then click Control Panel. Double-click Administrative Tools, and then double-click Computer Management.)

In the console tree, click Disk Management. (Under computer Management/Storage/Disc Management)
Right-click on the drive and then click "Change Drive Letter and Paths".

To modify the drive letter, click it, click Change, click the drive letter you want to use, and then click OK.

Important!!- Be careful when making drive-letter assignments because many MS-DOS and Windows programs make references to a specific drive letter. For example, the path environment variable shows specific drive letters in conjunction with program names.

Also note that you need to be logged on as an administrator or a member of the Administrators group in order to do this. If your computer is connected to a network, network policy settings might also prevent you from completing this procedure.