How to move or delete differencing disk?

[yitzhakbg]

I would greatly appreciate assistance in straightening out this disk problem. Please be patient if the question sounds longwinded. It's complex to me and I've included as much information as | could
I have two VMs:
One called Ubuntu 9.04, as follows:

General
Name: Ubuntu 9.04
OS Type: Ubuntu
Base Memory: 762 MB
Video Memory: 128 MB
Boot Order: Hard Disk, CD/DVD-ROM
ACPI: Enabled
IO APIC: Disabled
VT-x/AMD-V: Enabled
Nested Paging: Enabled
PAE/NX: Enabled
3D Acceleration: Enabled

Hard Disks
SATA Port 0: Ubuntu810shablona.vdi (Normal, 103.38 GB)

CD/DVD-ROM
Image: VBoxGuestAdditions.iso

The second VM is called Ubuntu 8.10. It's details are unimportant, since it's not used and it's disk is marked "unattached", but it does have a snapshot with the following detail:
Hard Disks
SATA Port 0: Ubuntu810shablona.vdi (Normal, 103.38 GB)
which is the disk listed above as Ubuntu 9.04's disk.

Now to the problem:
I'd just as soon delete Ubuntu 8.10 altogether, but due to some monkeying around in the past, the disk structure is inextricably tied to to Ubuntu 9.04 like Siamese twins.
Ubuntu 9.04 has the disk listed above (Ubuntu810shablona.vdi) marked as it's main disk. When I click on "show differencing disks" in the details of the disk menu, it shows:
C:\Documents and Settings\yitzhak\.VirtualBox\Machines\Ubuntu8.10\Snapshots\{f39514fb-db28-4d71-9ca3-018bb3b7def5}.vdi of type differencing (VDI) and attached to Ubuntu 9.04.
So Ubuntu 9.04 now has two disk images, "Ubuntu810shablona.vdi" and "{f39514fb-...}.vdi", but really doesn't need them both and we have to free up space on Windows disk C: where {f39514fb-...}.vdi lives.
For the life of me I can't either delete or move {f39514fb-...}.vdi. It's Ubuntu 9.04's lifeline.
How can I reduce the use of these two disks to only one which does not live on Windows disk C:?

Following is the output of VBoxManage showhdinfo for each of the two disks:

C:\Program Files\Sun\xVM VirtualBox>VBoxManage showhdinfo d:\ubuntu810shablona.vdi
VirtualBox Command Line Management Interface Version 2.2.2
(C) 2005-2009 Sun Microsystems, Inc.
All rights reserved.

UUID: 5efe8a61-4046-4eeb-bfbd-ff05177066d2
Accessible: yes
Logical size: 105865 MBytes
Current size on disk: 11158 MBytes
Type: normal (base)
Storage format: VDI
In use by VMs: Ubuntu8.10 (UUID: 1f2a6235-ab0e-463a-b1b7-0e6567803c3e)
Location: D:\Ubuntu810shablona.vdi

C:\Program Files\Sun\xVM VirtualBox>VBoxManage showhdinfo "\Documents and Settings\yitzhak\.VirtualBox\Machines\Ubuntu8.10\Snapshots\{f39514fb-db28-4d71-9ca3-018bb3b7def5}.vdi"
VirtualBox Command Line Management Interface Version 2.2.2
(C) 2005-2009 Sun Microsystems, Inc.
All rights reserved.

UUID: f39514fb-db28-4d71-9ca3-018bb3b7def5
Accessible: yes
Logical size: 105865 MBytes
Current size on disk: 11238 MBytes
Type: normal (differencing)
Storage format: VDI
In use by VMs: Ubuntu 9.04 (UUID: e5333aa5-fbc6-4488-986a-f846fcbc0f40)
Location: C:\Documents and Settings\yitzhak\.VirtualBox\Machines\Ubuntu8.10\Snapshots\{f39514fb-db28-4d71-9ca3-018bb3b7def5}.vdi
Auto-Reset: off

[vbox4me2]

Create a new VM disk and clone(clonezilla) which OS you want to save, delete the lot and attach cloned VM disk(s).

[yitzhakbg]

Thanks very much. That sounds like very practical advice. I must have gotten so wrapped up in my problem that I was barking up a complicated solution.
Kindly go over this together with me to make sure I've got it right. My understanding is that I have to:
1. Create a new VM disk (with the GUI interface or VBoxManage?).
2. Download the CloneZilla iso and boot from it.
3. At this point, there should be three disks attached to the machine: the original, the new one and the Clonezilla iso from which the machine is booted.
4. Perform the clone with Clonezilla from the old to the new.

Did I get it right?

[vbox4me2]

Yep, thats about it, unless you copy the wrong one making a backup isn't overkill here.

[yitzhakbg]

Thanks again. I'll give a shot tomorrow