1. Windows Genuine Advantage
This Vista feature is designed to combat piracy, but instead it wages war against common sense. If WGA believes that you aren't running a legitimate copy of Windows, it takes a variety of actions against you. In earlier iterations, it could in essence shut off your access to the operating system. Today, WGA isn't quite so draconian. Still, the real pirates know how to get around WGA, so it serves no purpose other than to annoy. Microsoft should get rid of it in Windows 7.
2. The Registry
The Registry is a giant, incomprehensible database of Windows settings, preferences, behaviours, and more. When you use a dialog box to make a change to how Windows works, generally it's making a change to the Registry --- often dialog boxes are mere front ends to the Registry. But to make many changes, you need to edit the Registry, and it's a tough, dangerous thing to do. Other operating systems, including Mac OS X and Linux, don't have Registries, and they work fine. It's time for Microsoft to finally kill the Registry.
3. ActiveX Controls
ActiveX controls are essentially applets delivered via Internet Explorer. They don't, however, run in other browsers. And they have the potential to be malicious. Once upon a time they served some use, but no longer. Given the growth of AJAX and Web 2.0 sites, it's clear that sophisticated applications can be delivered via the browser without ActiveX. Microsoft should finally pull the plug on this technology.
4. User Account Control
This is clearly the unanimous choice for a feature that needs to bite the dust. Sure, it offers security...but at far too high an annoyance cost, with pointless pop-ups and ridiculous intrusions. Microsoft needs to kill UAC and start from scratch.
5. Windows Meeting Center
Have you ever heard of this Vista feature? Likely not. And even if you have, you haven't used it. It's supposed to let you set up meetings over a network or the Internet either on an ad hoc or planned basis. But with no whiteboard, a worthless chat module, and no VoIP, who would ever use it? No one, of course. It's a waste of bits --- let it go.
Source : here