I bought a Seagate Go Flex 3TB External HDD w/ USB 3.0 interface, STAC3000101. I tried to shrink the drive and ended up with an unallocated sector with no options available. I cannot create or delete New Simple Volume. All I could see is just the properties which indicated the drive as 750G. The partition with 2TB seems fine. I could shrink the 2TB to 2 split 1TB partitions but the 750G was not even accessible. I tried deleting the total volume and re-partitioning it again. I still can't see the 750G. I could only see 2TB. It seems that I could only access 2TB and not the rest. What is going on here? Is this a manufacturing disk error or is something to do with the partition restrictions or set limit storage capacity of Windows Vista? How can I get back my missing 750G bytes free space? Is there any other Windows or operating systems which can solve this problem?
I don't know if this will help anyone, as it has been about 7 months since the first post, but I've been fiddling with a new WD external 3TB drive and have had similar problems.
One thing to check is when you are in the disk management screen, the box on the left that tells you the disk number, size, and type of drive has a menu if you right click it. If it has an option for converting to a GPT disk, then it is probably formatted as an MBR disk, which won't allow 3TB partitions due to the sector size limitations. What you would want to do is select the option to convert it to a GPT disk (Make sure you have all your data backed up as you will have to reformat the drive and lose everything) and create a new single 3TB partition.
First, you'll have to delete your 2TB partition. This will allow you to select the GPT option (it's greyed out if you have formatted partitions) and will create a single unformatted partition. Once it's done reconfiguring you can create a new simple volume using the wizard. I would leave everything default except the name of the drive and do a quick format. It should format in a minute or less depending on the speed of your computer. Now you have one big 3TB partition again! Woohoo!
Hope that helps.