Since some people found it useful, i thought i could upload it here, making it easier to find :p
Threw together a guide on how to recover and change/edit your serial-key, hopefully it helps
To view your cd-key there are several options, but to view the one your actually using you have to enter 'regedit' (look under 'Editing your serial-key' to see how) . Jump directly to the 'Editing your serial-key' if you are sure you got your hands on the correct cd-key.
RecoveryThe first and easiest step to view the serial-key you bought, is to go to their main webpage -> view games -> view serial-key. However to do this, your forum-account most be connected to your key.
Most likely you will not find your key on the webpage, as few people go through the trouble of adding it. But fear not, if you have bought it directly from TW, they have sent you a mail, which you can find easily by typing in the company name (two options: Avagate or eSellerate) in the search field:
Email (hotmail):
If you got it through steam, you can find your key by doing this;
If all of the above fails or you find this option easier, you can follow TW's serial recovery;
Editing your serial-keyStep 1: press the windows button or start
Step 2: In the search/run field type "Regedit"
Step 3: Locate HKEY_CURRENT_USER and double click it
Step 4: Double click software
Step 5: Double click Mountandbladekeys
Step 6: Double click serial_key & add the key connected with your character
Good luck =D