Increase the size of your Boot drive, your C Drive. This can be done without a server reboot on Windows Server 2012. In this video, I increase the size of the C drive on a Windows Server 2012 Standard. This server was installed on an 80GB partition (shows as 77GB). There was still 40+ GB free so I increase the size of the drive to 100GB. If you have any issues extending your C drive, go to Tools\Computer Management and then click Storage and then Disk Management. Look at the available space directly next to the C drive. It should say unallocated. If you have a D drive partition directly next to C, then you probably won't be able to extend the C Drive, instead try extending the D Drive.