Go the Start > Administrator Tools

Go to [Disk Management]. Notice you have [Unallocated space] for your disk.

Right click on the [C:] drive and choose [Extend Volume].

Click [Next].

Click [Next]. Note: The [Select the amount of Space in MB:] should match the [Maximum available space in MB:] to utilize all the unallocated disk space.

Click [Finish].

Done. You have extended the disk to utilize all available disk space.