I've been using Vista since its beta days. There were numerous incompatibilities when it first launched. Over time, many of these issues have disappeared. If someone is moving to Vista they should also make sure that they are using the latest version of any other software. Most software companies, that still exist, have released updated versions that run on Vista.
Many users do not know that Microsoft has a downgrade option that allows you to use XP without buying a license for it, if you own Vista.
Specifically, these downgrade rights lets owners of some versions of Vista replace it with Windows XP without having to pay for another license. In effect, the license for Vista is transferred to XP. Think of it as a swap, Vista for XP, not as an extra license. By Microsoft's end-user licensing agreement (EULA), you can't have both the Vista and its downgraded XP installed at the same time on the same or different machines. You have to pick: It's one or the other.
What is a downgrade? To Microsoft, "downgrade" describes the licensing rights it grants to older operating systems. Downgrade doesn't mean the process for rolling back Windows from Vista to XP, since there isn't such a procedure, not in the generally accepted use of "upgrade." In an older-to-newer move, developers usually make it possible to retain all the digital detritus on the drive, from already-installed applications and Word documents to iTunes tracks and family photos, while updating the system files. Not so in a downgrade.
So, what downgrades does Microsoft allow? Owners of the OEM editions of Vista Business and Vista Ultimate can downgrade to Windows XP Professional, including Tablet PC Edition and x64 Edition. Only the OEM editions qualify for a downgrade, so if you purchased a new PC with either Business or Ultimate preinstalled, you're in like Flynn.
How do I downgrade? Install a copy of Windows XP Professional with the product key that came with the copy, and then when you hit the activation screen -- which is near the end of the installation process -- select the activate by phone option rather than the online method. You'll likely end up talking with a live rep; tell him that you're downgrading from Vista to XP, and give him the Vista product key. The rep is supposed to walk you through the rest.
You can find out more at: http://www.computerworld.com/action/article.do?command=viewArticleBasic&articleId=9040318.
The issue with compatibility is not always Microsoft's fault. Many times the issues lie with the software developer that wrote the 3rd party application. Programmers will often take steps around the preferred Microsoft way to get their application to run faster or to decrease development time. With newer upgrades to Windows these workarounds no longer function.
I just read a story on this a couple of days ago:
Microsoft Corp. CEO Steve Ballmer offered a glimmer of hope on Thursday to fans of the company's Windows XP operating system, saying the company may reconsider its decision to stop selling it soon.
But Ballmer was adamant that most people who buy PCs today buy them with XP's successor, Vista.
"That's the statistical truth," he told reporters at a news conference at Louvain-La-Neuve University. "If customer feedback varies, we can always wake up smarter."
Fans of XP - the 6-year-old operating system set to be pulled off store shelves by June 30 - have plastered the Internet with blog posts, cartoons and petitions. They trumpet its superiority to Vista, whose consumer launch in January was greeted with lukewarm reviews.
Ballmer said the customers buying PCs with XP are corporate information technology departments that are having trouble shifting old machines to newer technology.