The Wikipedia contains a fascinating article, “Features removed from Windows Vista,” describing things that were in Windows XP that aren’t in its successor.
The long list of removed features is broken up into 15 main categories:
1 Windows Shell
2 Windows Explorer
3 Internet Explorer
4 User account rights and logon
5 Win32 console
8 File system, drivers and memory
9 Boot, shutdown, power management
10 Windows applications and features
11 Legacy applications and features
12 Graphics, DirectX and video
13 Installation and servicing
15 Other minor changes
As someone who uses Window XP and Windows Vista only occasionally these days, I haven’t noticed many of these things myself. Regular Windows user may know most of this stuff.
It is noteworthy that Microsoft removed Services for Macintosh, which provided file and print sharing via the obsolete Appletalk protocol. This could affect Windows Vista users on a network that has old Appletalk file servers and printers.