vmkfstools -X 10G disk1.vmdk will extend disk1.vmdk to 10GB You will then need to let windows know that it can use the entire disk - if it isn't a boot or system disk then this is easy. You simply go to the command prompt run diskpart. Select the disk then the volume and run extend. If its a system disk or got the page file. You need to either boot off of a bartpe cd and run the command or temporarily attach it as a secondary disk to another VM and run the same command. If like me you get.. Failed...