Whenever you upgrade the memory on a Windows Cloud Server, you’ll notice that, although the memory has increased, the disk space has not. This happens because the hypervisor uses a sparce disk file for the virtual hard drive on Windows instances. Since the hypervisor is unable to access the partition structure inside this file directly, the additional drive space that is allocated to your server after the resize must be manually managed within the OS itself.
Before making any changes to your partition structure, make sure you take a backup! Any kind of mistake or problem during this process will render your machine unusable!
On Windows 2008, this can be accomplished quite easily with the built-in tools. After the resize operation has been completed and the Rackspace control panel has asked you to verify the integrity of your server, you can follow these steps to expand the partition: