Ubuntu - Pendrive - VM or Boot option

[Patton Echols]

Apologies if this is a double post.  I don't see the original

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Greetings:

I have been reading about ubuntu on a pendrive:

  Here:
https://wiki.ubuntu.com/LiveUsbPendrivePersistent
 and here:
http://rudd-o.com/new-projects/portablelinux

It all looks rather "doable".  

There are also some threads about running a pendrive linux under a 
running windows here:

http://www.pendrivelinux.com/category/virtual-machine/

But it appears that you have to choose your boot method when you create 
the pendrive.  What I am working on is a project that would be useful to 
be able to do both - either boot from the drive, or run in  a VP under 
Win XP, or Run in a VM under linux.  The choice would be made at the 
time.  Example:  You're at home and want to run this install, simply 
reboot the machine . . . Example 2: You're at work and need to run under 
WinXP because there are others accessing resources on your machine even 
though it is lunchtime.  Example 3.  You're back home again, and need 
something off of the pendrive, but don't want to restart the linux box 
because it is also your spouse's printer server . . .

Anyone know of a "Duh, why couldn't he find that" website that addresses 
this?  Any other comments?

Thanks
--P