Migrating a virtual machine to another host

[ZioNemo]

Sorry if I'm asking something obvious,
this should be a FAQ, but I wasn't able to find a definite solution.

I have a virtual Machine: ubuntu host, ubuntu guest, several snapshots I do not want to lose.
I need to run this machine (or a complete clone) under another OS (Windows Vista, in this case).
Is this possible?
Ideally I would like to be able to put my VM on an USB stick and run it anywhere, but I fear that isn't possible as the xml contains guest-related info (why? the machine should be independent from the host. VMWare machines surely are).

Can someone point me in the right direction, please?

Thanks in Advance
ZioNemo

[vbox4me2]

Copy everything over, vdi, snapshots, xml files in exactly the same location. Between Host OS's you'll need to edit all xml's to reflect the file system.