|"there is a terabyte of work|
on this particular hardrive". Please help!
In the future, help yourself by keeping copies of all your personal files. If you need to add additional hard drives then do so.
In my opinion the most reliable backup method is to save the files to DVDR. If you wait until you have 1TB of data it may take quite a while to burn that much data.
The amount of effort you should put into keeping copies of personal files is inversely proportional to the importance of the files. Irreplaceable files like photos or manuscripts should be treated with even more card. Multiple copies including off site storage.
Why were you trying to boot from a flash drive to start with? Was there a problem with your Windows installation?