xVM's vboxmanage.exe command

You can view and edit the configuration of your guest OSs using the vboxmanage command. To view the list of guest OSs you have, give the following command:

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

"MySolaris" {dc6dc85f-5583-4a1b-bf3e-969941a2cd91}
"Ubuntu" {eb973bbf-d86e-4579-85eb-6ea2cd12bf95}
"Debian" {3e784597-89d8-4f17-90cb-63e866c651a3}
"openSUSE" {6862884e-60e1-4c65-8aab-b57ec38a3922}
"Debian-Lenny" {4b561432-abac-4a27-a501-b42af956b96b}

To view the specific guest, you can use the UUID of the guest. For e.g.

C:\Program Files\Sun\xVM VirtualBox>VBoxManage.exe showvminfo eb973bbf-d86e-4579-85eb-6ea2cd12bf95
VirtualBox Command Line Management Interface Version 2.2.2
(C) 2005-2009 Sun Microsystems, Inc.
All rights reserved.

Name: Ubuntu
Guest OS: Ubuntu
UUID: eb973bbf-d86e-4579-85eb-6ea2cd12bf95
Config file: C:\Documents and Settings\roy\.VirtualBox\Machines\Ubuntu\Ubuntu.xml
Memory size: 512MB
VRAM size: 12MB
Boot menu mode: message and menu
ACPI: on
...

Remember a couple of things:
1) If you would like to view the guest OS by giving its alias, it is case sensitive. For e.g.

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

ERROR: Could not find a registered machine named 'ubuntu'
Details: code VBOX_E_OBJECT_NOT_FOUND (0x80bb0001), component VirtualBox, interface IVirtualBox, callee IUnknown
Context: "FindMachine (Bstr(VMNameOrUuid), machine.asOutParam())" at line 1921 of file VBoxManageInfo.cpp

But the same command worked fine when I gave "Ubuntu" (without quotes) as argument.

2) If you would like to specify UUID, rememeber not to include curly braces ("{}") .

To know all the available options, you can just give the vboxmanage command. That will list you all the available operations.