IT managers are facing a perfect storm of Windows upgrade options.While the Windows 7 beta has garnered some of the operating system's best reviews, many IT managers happy with Windows XP are not itching to upgrade, particularly in an economic downturn.XP is running on 71 percent of business PCs, according to a Forrester survey of 962 IT decision-makers, yet a momentum shift is slowly taking place. \n\nOverall market share for Windows XP has dropped 10 percent in the last year, while Vista has gained the same percentage, according to Web metrics company Net Applications. Also, the same Forrester report reveals that plans for Vista deployments in enterprises are on the rise;31 percent of survey respondents said they have already begun their migrations to Windows Vista.Time will tell if such Vista upgrade plans will be scrapped with the economy faltering, but XP users need to start planning now as they face a swirl of options: Upgrade to Vista now as a bridge to the similarly architected Windows 7; wait for Windows 7; try a mix of XP, Vista and Windows 7; stick with Windows XP and worry about upgrading later.CIO.com caught up with Gavriella Schuster, Microsoft's Senior Director of Windows Product Management, who discussed five points that enterprises should consider when making a Windows upgrade.(For more Windows upgrade guidance, check out the new "Windows for your Business" blog.)Windows 2000 Headed for Dinosaur-LandFor the very few of you still running Windows 2000 (which has 1.37 percent market share, according to Net Applications), the clock is ticking.Shops still running Windows 2000 need to upgrade as soon as possible to Windows Vista, given that extended support for Windows 2000 ends in Q2 of 2010, Schuster says. "Windows 2000 users are going to find that may of their applications have already run out of support from their application vendors. They need to make that change if they haven't done it already," says Schuster.If You're Moving to Vista, Don't StopFor the 31 percent of the 962 IT decision-makers from the Forrester report who are planning to migrate to Vista (and for any other Vista migrators out there) Schuster says, continue on your merry way."Vista migrators are in good shape; they should keep moving that way," she says. "We are setting them up to have an easier migration to Windows 7 when they want to do it because of the high degree of compatibility between the two operating systems." Schuster also recommends that if you are in the early stages with a Vista migration, you should plan to test and deploy Windows Vista SP2, which is targeted to release to manufacturing in Q2 of 2009. Undecided XP Users: Set a Game PlanIf you're an XP user who has no concrete upgrade plans (30 percent, according to Forrester), Schuster warns of the risks of skipping Windows Vista. For instance, you may find yourself with applications that are no longer supported on XP and not yet supported on Windows 7.Because of this possible application no-man's-land, Schuster says XP customers should know how many applications they have, test to see how many are compatible today, and talk to application vendors about when support will run out and when they will start supporting Windows 7."Businesses have between 500 and 5,000 applications, so there's a lot of testing to be done there," says Schuster. "They should test them on the Windows 7 beta or Windows Vista. It doesn't matter which because they are compatible, but users should start identifying which applications don't work."Another option for those undecideds: have a heterogeneous environment that runs XP, Vista and possibly Windows 7 machines for a year or two before making a full migration to Windows 7. Dont Wait in the Dark for Windows 7If you're set on waiting for Windows 7, waiting is what you shouldn't be doing, says Schuster."You should start the process with Windows 7 now, by looking hard at the beta and testing your applications to see which ones are compatible with Windows 7," she says. If XP users aren't sure if their apps are compatible with Windows 7, they should test them with Windows Vista because "if they're not compatible in Vista, they won't be compatible in 7," she advises.Also, XP users should consult with their application vendors to make sure that their applications are compatible, or understand what their vendors' support policies are."After all this they should start their Windows 7 deployment now with the knowledge that it will take 12 to 18 months to get it done," Schuster says.Deploy The Desktop Optimization PackSchuster recommends deploying the Microsoft Desktop Optimization Pack (MDOP) regardless of which OS you are running today or plan to deploy. MDOP is a suite of six products that help manage PCs and are available to businesses using Microsoft's Software Assurance maintenance program at an additional cost. It has been available since January 2007 and more features have recently been added through acquisitions of virtualization companies Softricity and Kidaro.Products folded into MDOP aim to help IT departments reduce the time and money it takes to test and deploy new applications. These additions include Enterprise Desktop Virtualization, which uses OS virtualization to support legacy applications that are not yet ready to migrate to a new version of Windows, and Application Virtualization, which enables applications to be installed on PCs so that they are isolated from other applications and from the OS itself.It's understandable that cash-strapped IT managers may see MDOP as Microsoft forcing software upon them. But Gartner did release a report in July 2008 analyzing the benefits of MDOP, praising the price of $7 to $10 per user per year (even if it is on top of the SA price of $30 to $40 per user per year) and stating that the use of a single MDOP feature could justify the cost of the whole pack for some customers.However, Gartner does advise that you compare the features in MDOP to similar products from companies such as VMWare, Citrix and Altiris.