Windows XP was built upon Windows 2000, which in turn was built upon Windows NT 4. No version of Windows has ever been "redesigned from scratch" in the way that Mr Monstermunch is suggesting. Vista is built upon Windows Server 2003, although the massive changes to that OS have earned it the NT version 6.0 tag.
XP doesn't hold the crown to the single biggest update to Windows either, and never did. It was just a skinned version of Windows 2000 with some other improvements. Most people will say Windows 2000 was the best update to Windows, because it brought about a usable and rock solid stable OS. But people who've been in the game a bit longer
will say Windows 95 was the biggest update. Because that of course added all the things we take for granted today, such as plug'n'play, the taskbar, the basic Explorer shell. Sure in hindsight it may have been an unstable and relatively badly received update to Windows but back then when this stuff was still new it was awesome.
Jokester said:
What's Microsofts plans as regards DRM with Vista?
Contrary to popular belief their plans are actually very small. They are doing the bare minimum to keep the RIAA and MPAA happy. They have also added some of their own optional features such as the BitLocker encryption. This uses a TPM module's key to encrypt your files on NTFS. It is basically just a more secure version of the encryption already available in NTFS. It isn't a form of DRM though because 1) it's optional 2) it doesn't restrict _your_ access to _your_ files - it only prevents others from accessing your stuff...
Windows Media Player is sure to see some DRM enhancements (upon what it has already that is) to keep media suppliers happy.