Where are the files you want to recover?
At first it sounded like the files you wanted to recover were on the internal hard drive of the computer. To recover those, you'd need to boot from a CD or DVD or flash drive so you could copy those. Ubuntu or BartPE would what you'd need on these discs. If you wanted to copy from the internal hard drive to the external drive, you could then do it because you'd have an operating computer. Both Ubuntu and BartPE give you an operating computer you could use to access the files on the internal hard drive and copy to the external one. You would just use copy and paste or drag and drop, just like you would if you'd booted Windows Vista.
Later in this thread it sounded like you wanted to recover files from the external hard drive. In that case there's no need to copy anything because reinstalling isn't going to destroy anything there.
I think you need to be specific about where you want to copy FROM and where you want to copy TO.