Windows 7 ultimate features that are not given in Windows Home premium:
* XP Mode. This runs a virtual machine on Windows 7, it very literally is like having a dual boot windows xp/windows 7 without the hassle. You could run into driver issues, particularly with graphics, and usb devices.
* BitLocker. This software is useful for encrypting, and lock hard drive partitions.
* Domain Join (Professional version has this aswell). Advanced networking, usually for connecting many computers in an office securely (home premium can do this as well, however it is prone to security issues which could be patched but require advanced networking capabilities to implement).
* Backup and Restore. This is a very important feature (professional has it as well) because it saves previous versions of folders, create backup files, as well as restore from backups. This is incredibly useful, I have often messed with some programs to tweak them and caused irreparable harm I used restore previous version to fix them.
* Languages: Speak mandarin? No problem. spanish? No problem. Speak another 33 languages? No problem. These are GUI language packs. Meaning everything inside windows will be translated.