Keeping up interest in existing products is one of the biggest challenges faced by companies with better stuff in the works. Microsoft is grappling with that big time these days with Windows Vista -- given the global economic turmoil, all the positive reviews for the Windows 7 Beta, and the not-so-subtle hints that the new operating system will be done this year.

Today the company is releasing its official "deployment guidance" for big businesses that are now in a position to upgrade their desktop computers from Windows XP or (gasp) Windows 2000. Can you guess what it's recommending?

In an interview at Windows headquarters earlier this week, Microsoft's Gavriella Schuster cited Windows Vista's stronger security, and lower technology management costs realized by companies that run Vista in conjunction with Microsoft's Desktop Optimization Pack.

"It is a good operating system, and it's stable," Schuster said. "One of the things customers have been asking me is, 'If I make an investment in Windows Vista today, is it a throwaway investment?' And the answer is no. It's not a throwaway investment."

Windows Vista introduced a series of security changes that made the transition from older operating systems difficult, especially at launch, when many device drivers and software applications hadn't caught up. The leap in compatibility from Windows Vista to Windows 7 is smaller. In essence Microsoft is encouraging most companies to go ahead and get it over with by moving to Vista now.

Read on for Microsoft's guidance to businesses in different situations, and offer your take in the comments below.

Running Windows 2000 Professional: Microsoft Windows 200 PCs to Windows VIsta as soon as possible. Windows 2000 extended support ends Q2 2010. Windows 2000 customers may soon find their business critical applications unsupported.

Windows Vista deployment in progress or planning: Continue your Windows Vista SP1 deployment. If in early stages or just starting on Windows Vista , plan on testing and deploying Windows Vista SP2. Easier future transition to Windows 7 due to high degree of compatibility.

Running Windows XP, undecided about Vista: Make sure you are aware of the risks of skipping Windows Vista -- such as running out of ISV support for your critical business applications. Deploying Windows Vista will make future transition to Windows 7 easier.

Running Windows XP, waiting for Windows 7: Start early evaluation of Windows 7 for your company with Windows 7 beta. Tesing and remediating applications on Windows Vista will ease Windows 7 deployment due to high degree of compatibility."