Virtual Disk size increase not showing in Windows 8.1

[madskier]

VirtualBox Version 4.3.12 r93733
Mac OS-X 10.9.5
Guest OS: Windows 8.1
Guest additions: 4.3.12

Attempting to increase the size of a virtual disk (VDI type). Everything indicates it worked on the VirtualBox level (see status, resize and status outputs below), BUT in Windows the new space doesn't show up (See diskpart output below). I have rebooted the Guest several times. I deleted my snapshots before attempting the resize. I have also tried re-installing the guest additions.

I know about using Computer Management -> Disk Management and extending the volume, as I have done it Many times before. Usually the extra space shows up and then you can click "Extend volume", but if Windows doesn't see the extra space, it grays out the 'Extend Volume' option, which is the case I have here. Anyone know what is going on here?

MacBook-Pro:~ $ VBoxManage showhdinfo VirtualBox\ VMs/Windows81/Windows81.vdi
UUID: c25855ef-4a34-4c17-a096-5ee932aa5145
Parent UUID: base
State: created
Type: normal (base)
Location: /Users/madskier/VirtualBox VMs/Windows81/Windows81.vdi
Storage format: VDI
Format variant: dynamic default
Capacity: 51200 MBytes
Size on disk: 31544 MBytes
Child UUIDs: b1a4a8cd-0545-497f-b037-a4002c7d8008
MacBook-Pro:~ $ VBoxManage modifyhd VirtualBox\ VMs/Windows81/Windows81.vdi --resize 75200
0%...10%...20%...30%...40%...50%...60%...70%...80%...90%...100%
MacBook-Pro:~ $ VBoxManage showhdinfo VirtualBox\ VMs/Windows81/Windows81.vdi
UUID: c25855ef-4a34-4c17-a096-5ee932aa5145
Parent UUID: base
State: created
Type: normal (base)
Location: /Users/madskier/VirtualBox VMs/Windows81/Windows81.vdi
Storage format: VDI
Format variant: dynamic default
Capacity: 75200 MBytes
Size on disk: 31544 MBytes
Child UUIDs: b1a4a8cd-0545-497f-b037-a4002c7d8008


Microsoft DiskPart version 6.3.9600

Copyright (C) 1999-2013 Microsoft Corporation.
On computer: WINVMONMAC

DISKPART> list disk

Disk ### Status Size Free Dyn Gpt
-------- ------------- ------- ------- --- ---
Disk 0 Online 50 GB 0 B *

DISKPART> select disk 0

Disk 0 is now the selected disk.

DISKPART> detail disk

VBOX HARDDISK
Disk ID: 27DEE6C1
Type : SATA
Status : Online
Path : 0
Target : 0
LUN ID : 0
Location Path : PCIROOT(0)#PCI(0D00)#ATA(C00T00L00)
Current Read-only State : No
Read-only : No
Boot Disk : Yes
Pagefile Disk : Yes
Hibernation File Disk : No
Crashdump Disk : Yes
Clustered Disk : No

Volume ### Ltr Label Fs Type Size Status Info
---------- --- ----------- ----- ---------- ------- --------- --------
Volume 0 C NTFS Simple 49 GB Healthy Boot
Volume 1 System Rese NTFS Simple 350 MB Healthy System

DISKPART>

[socratis]

I deleted my snapshots before attempting the resize.
...
UUID: c25855ef-4a34-4c17-a096-5ee932aa5145
Parent UUID: base
...
Child UUIDs: b1a4a8cd-0545-497f-b037-a4002c7d8008

From the FAQ: How to resize a Virtual Drive. You seem to break rule #1; it seems that you have a snapshot.

PS. BTW, I really don't know why the "(Prior to 4.3.*)" is in the linked article. I don't recall any change in that area and the rule always was "Don't use snapshots".

[mpack]

PS. BTW, I really don't know why the "(Prior to 4.3.*)" is in the linked article. I don't recall any change in that area and the rule always was "Don't use snapshots".

In 4.3.0 the devs fixed a bug that made it impossible to resize drives that used snapshots. Now it is possible, but it still isn't a good idea because of the likely confusion such as the OP is showing (resizing the base VDI, which is currently not directly used in the VM).

[socratis]

Aha, I see. So, just to make it clear, if I were to increase the size of a dynamic VDI with snapshots, I would go about that by resizing the last snapshot? Not that I would (DANGER! DANGER!), just out of academic curiosity...

[mpack]

Yes, exactly so. I'm not greatly experienced with snapshots, so don't ask me what happens if down the road you then do something like delete an intermediate snapshot (i.e. where there needs to be manipulations between VDIs having different sized block tables).