What exactly happens after OS is restored to a USB-connected hard drive?

Sorry, newbie question here:

Once I use Paragon Backup and Recovery 2011 (Free) to restore/recover my C:/ drive to a USB-connected hard drive, and want to run all my programs for a while from that external drive (just to confirm successful backup imaging) ... how do I tell my computer to use the OS from the external drive, not the original C:/ drive in my desktop?

And similarly, how do I tell it to run all my programs, (Windows, Firefox, Excel, etc.) from the external hard drive, not the "original" C:/ hard drive?

Thanks much, I appreciate your patience!

 

Try it, you'll like it.

Judt set your BIOS to boot from the USB drive after recovering into it, the USB will become the C: drive, the system will assign the old HDD C: a new unused letter and start normally.

 

AFAIK, Windows can´t boot from an external USB disk.

 

That is my understanding as well but I thought perhaps there was some Paragon magic I don't know about.

 

I think as long as the USB drive shows in your BIOS, it will. In fact, I made a RAW copy to a USB drive, tried to boot from it, a sreen came up asking if I wanted to change the hardware config or something. I chickened out then but appeared that Windows was going to allow it.