Windows 7 may not be best suited to a tablet interface, but when you need to run software that works only on Windows, a Windows tablet is what you need. Another advantage of such a tablet is that you'll get all the familiar security tools you're used to working with. Many Windows tablet manufacturers are including hardware security features such as fingerprint readers and SmartCard slots as well.
Windows 7 comes with Windows Defender, User Account Control, a built-in Backup and Restore program and a firewall. Your device can join a domain with the Professional and Ultimate editions. The Ultimate and Enterprise versions also come with BitLocker for full hard-drive encryption.