If you have a Toshiba with AuthenTec biometric device and you forgot to clear the fingerprints before formatting your windows 8.1 installation, you will face the issue of not being able to register the same fingers in your newly created Microsoft Account. The issue steams from the buggy implementation of the Toshiba Fingerprint Utility that doesn't handle domain accounts that well. Moreover, the fingerprint biometric data are stored inside the hardware, so no matter what file you delete, you won't be able to fix this. Some people on the net report that a simple export and import of the data (using the utility as administrator) worked for them. All the reports were mentioning windows 7 so I guess they were all facing an issue with local accounts and not domain ones.
Luckily, Toshiba discovered the issue and offers a command line tool to delete all fingerprint data from the hardware. The name of this tool is TFPU WBF Delete Fingerprint Tool (a.k.a. tc30636900b.exe) and this made the trick for me.