Time ago Internet Explorer got out and began being integrated deeper and deeper into the operating system. Now we had Windows Explorer for the inside and Internet Explorer for the outside, and we got Back and Forward buttons in our folder windows to navigate through files more easily, the way we got accustomed with the Web.

Also, the Location Bar in Windows Explorer that showed what directory (folder) on the hard disk we were working at, accepted the input of Internet addresses (WWW and FTP) and made Windows Explorer windows morph into Internet Explorer ones.

Then we had Web content embedded into the Desktop and “Web views” of folders, too, and more and more help guides and tutorials began looking like Web pages, when not being expressly made in HTML.

Now, what actually sparked this post, is that many options that were identified and accessed to by icons in Windows XP and previous incarnations, are now accessed through hyperlinks, just as if they were menus on a Web page. The funny thing is that on the same day I read a related article on Jakob Nielsen’s website, I got my first look at Windows Vista Basic, and faced the exact same usability issues he pointed out so well.

I guess this path of integration with the Web will just continue to grow, and the dividing line between the desktop GUI and the Web GUI will disappear eventually, with more and more applications now available from the Web and the value of non-networked PCs being close to nil. The network is the computer, said the visionaries at Sun years ago, and only now we are really getting it.

1. Use the Aero Theme and System Font (Segoe UI).
   That means: do not invent the wheel all over again, use the Windows Vista standards, at least if you are not trying specifically to give your application a distinctive look and feel (if so, bear in mind that usability drawbacks may arise).
2. Use common controls and common dialogs.
   Again, users are accustomed to the way things work in Windows. Good or bad, give them what they expect or they may get confused and lose otherwise productive time on doing standard tasks.
3. Use the standard window frame, use glass judiciously.
   Transparency (glass) in windows may look nice, but it may lead to users not really knowing which controls belong to which window. More is not always better.
4. Use icons and graphics consistent with the Windows Vista style and quality.
   Screens and graphic cards have improved so vastly since the Windows 3.x and Windows 98/95 era, that icons made with them in mind simply look bad in Windows XP, and awful in Windows Vista. If the icon is the face of your application, make it as nice as possible, so as users are pleased to look at it every time they use the software.
5. Use task dialogs for new or frequently used dialog boxes and error messages.
   Make the most out of every message you present to the user. Be clear. Do not make people guess, call a friend or run to the Web in search of a meaningful explanation of what is happening with their computers.
6. Use Aero Wizards.
   Say what needs to be said. Ask what needs to be asked. Make wizards only as long as you must. Give users the freedom to do as they please.
7. Use Explorer-hosted, navigation-based user interfaces, provide a Back button.
   The Web is the most used application nowadays, making the boundaries between Web and Computer-based applications increasingly blurred, so imitating standard Web navigation whenever possible for multi-step processes will only do you good.
8. Use the Windows Search model.
   Well, they call it the Windows Search model, yet one could argue it is the Google Search model, applied as the Opera/Firefox Web-browsers did long ago. No matter how you call it, you know what it means: search box in the upper-right and search results displayed as fast as possible.
9. Use the Windows Vista tone in all UI text.
   Watch your writing. Be friendly, yet direct. Be concise, yet meaningful.
10. Clean up the user interface.
    Clutter is all around, so fortunately for all of us, simplicity is in vogue. Organize commands and options hierarchically, make frequently used items more prominent, illustrate with text or icons if needed, use tips for mouse-overs and full keyboard access. In short, trim all the fat you can from your user interface.
11. Use notifications judiciously.
    Showing notifications too often, in non-standard Windows modes or with too much text in them that obscures the core message will only ensure they are ignored. Keep them useful by not making those mistakes.
12. Reserve time for “fit and finish”!
    “Perception is reality” says the Microsoft website, and they surely know what they talk about: they made billions out of this. In these times, your application must look nice in order to be taken seriously and to be granted more room for error.

For the complete info:
http://msdn2.microsoft.com/en-us/library/aa511327.aspx.