Restoring a Mac but maintaining the files

Restoring a Mac but maintaining the files

I've got an external hard drive which I've hooked up to time machine, I
have multiple Mac's but the one in question I am unable to remember the
administrator password, which is a pain when trying to create an extra
user account and install software, etc.
Is there a way of restoring the iMac (what's the best way to do this?) and
getting all my files back, including Microsoft Office (if I am correct
Time Machine will automatically back up software as well?) but is there a
way of setting up the mac once restored through TM keeping all the files
but not the user profile.
OR, what should I do in this situation? I don't really want to lug this
thing into London and back! What's the best way of keeping all my files
and existing software but be able to start up with a new user.