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In disk management does it show that the entire disk has been formatted? &nbsp;i.e. no unpartitioned space.
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Can you take a screen shot of Windows Disk Management and post it here? <br />
It could be that PartMgr driver did not update the partition size data for Windows Explorer. So you need to do it manually. For this in Windows Disk Management shrink the last partition for 1GB and then expand it again for 1GB.
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<a href="https://filedb.experts-exchange.com/incoming/2016/01_w02/1066665/MMC_Disks.png" target="_blank" title="MMC_Disks.png (37 KB)"><img alt="MMC_Disks.png" class="file-block lazyload" style="max-width: 800px;" data-src="https://filedb.experts-exchange.com/incoming/2016/01_w02/800_1066665/MMC_Disks.png" /></a><br />
In the bottom part of the screen you can see the U: Drive is 3549GB whereas on the top it is 1024GB.
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MMC_Disks.png

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Right click on U - shrink, shrink it for 200-300MB. Then press ok.<br />
After that again press right click on U and use Extend partition. Add those 300MB back. Refresh the MMC and see if it shows correct size in Windows Explorer.
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Illogical Captain, but I like it: Unfortunately it didn't work.<br />
<br />
Try to shrink but gave a &quot;Volume you have selected to shrink may be corrupted.&quot;.<br />
<br />
Couldn't chkdsk /f it as O/S was unable to unlock it.<br />
<br />
Removed the partition and then it shrunk the Volume down to 2TB!<br />
<br />
What is going on. New disk set up like textbook.<br />
<br />
<a href="https://filedb.experts-exchange.com/incoming/2016/01_w02/1066758/MMC_Disks_2.png" target="_blank" title="MMC_Disks_2.png (35 KB)"><img alt="MMC_Disks_2.png" class="file-block lazyload" style="max-width: 800px;" data-src="https://filedb.experts-exchange.com/incoming/2016/01_w02/800_1066758/MMC_Disks_2.png" /></a>
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MMC_Disks_2.png

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So, the problem is obvious, your drive is partitioned in MBR format and you need it to be in GPT format. You can do this in two ways:<br />
1) using Windows Disk Management (requires deleting all partitions)<br />
2) using third party tool such as Paragon Hard Disk Manager 15 Business which costs $300.<br />
<br />
If you can copy out data from D E and W then you don't need third party tool. Otherwise you have no choice and need to use third party tool.<br />
To check which format the drive is: <br />
1) right click on D <br />
2) select properties<br />
3) hardware<br />
4) select your big disk and click on Properties<br />
5) then select Volumes and finally press on Populate.<br />
You will see detailed information.<br />
What is partition style there? Mastet Boot Record?
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It's weirder than that, it really is GPT.<br />
<a href="https://filedb.experts-exchange.com/incoming/2016/01_w02/1066769/MMC_Disks_3.png" target="_blank" title="MMC_Disks_3.png (9 KB)"><img alt="MMC_Disks_3.png" class="file-block lazyload" style="max-width: 404px;" data-src="https://filedb.experts-exchange.com/incoming/2016/01_w02/1066769/MMC_Disks_3.png" /></a>
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MMC_Disks_3.png

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Yes, now I am scratching my head :)<br />
What is the real size of the drive? Is this RAID if yes then how many drives of which size and in which type?
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It's a WD Green 6TB 3.5&quot; SATA Desktop Hard Drive (WD60EZRX).<br />
It's 6TB that formats in at 5.4TB. It came up originally as correct but then began to implode.
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Can you download the WD Diag tool for this drive and test it? Does it show on BIOS as 6TB?
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This is getting into witchcraft territory!<br />
<br />
<a href="https://filedb.experts-exchange.com/incoming/2016/01_w02/1066802/MMC_Disks_4.png" target="_blank" title="MMC_Disks_4.png (76 KB)"><img alt="MMC_Disks_4.png" class="file-block lazyload" style="max-width: 626px;" data-src="https://filedb.experts-exchange.com/incoming/2016/01_w02/1066802/MMC_Disks_4.png" /></a><br />
Should I just pull stumps and ask them to replace it!
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MMC_Disks_4.png

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Please read the messages as this is a simple solution to what was a very rogue disk.
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<div class="content wysiwyg-content">
6TB disk setup with GPD.<br />
<br />
Disk broken down into:<br />

<div class="bullet">
1024GB
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<div class="bullet">
512GB
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<div class="bullet">
512GB
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<div class="bullet">
3544GB
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<br />
MMC reports all sizes as correct.<br />
The O/S sees all the smaller sizes but the last, largest partition it reports back as 0,99TB.<br />
<br />
What's happening?
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6TB disk setup with GPD.

Disk broken down into:
1024GB
512GB
512GB
3544GB

MMC reports all sizes as correct.
The O/S sees all the smaller sizes but the last, largest partition it reports back as 0,99TB.

What's happening?

SBS 2011 Downsizing Large Partition Sizes

Small Business Server (SBS) is a line of server operating systems targeted at small businesses by bundling the operating system with a number of other Microsoft products that would normally need to be purchased or licensed separately. The most notable inclusions are Exchange, SQL Server, SharePoint and ISA/TMG (Microsoft's firewall and proxy server).

Windows Server 2008 and Windows Server 2008 R2, based on the Microsoft Vista codebase, is the last 32-bit server operating system released by Microsoft. It has a number of versions, including including Foundation, Standard, Enterprise, Datacenter, Web, HPC Server, Itanium and Storage; new features included server core installation and Hyper-V.