Welcome to mobileread ....
Sorry about your problem, have a look in the Sony Forum (link main forum page), and perhaps post there.
Surprised that WHSmith thinks you have a 'new computer' when any other piece of software would, normally, not do so unless you changed some hardware components. Wonder what WHS is looking at ?
ADE of course ! (Thanks pdurrant)
If you have that much on your reader, if you can return them to the PC, then de-DRM them (unlock them) and transfer back....
[Try google search for solutions to remove DRM from your books - it's easier than it sounds 
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