Software giant Microsoft Corp. is hoping to erase the bad memories of its last major upgrade to the Windows operating system, Vista, with its release of Windows 7 this fall. The program has drawn several favorable initial reviews, but upgrading won't be without its challenges for schools still using Windows XP, some early testers report.

XP users could constitute a majority of schools and districts, experts say, because compatibility problems between Vista and other software applications caused many schools to forgo Vista in favor of the older XP operating system on their recent hardware purchases.

Compatibility should be less of an issue with Windows 7, Microsoft promises, thanks in part to a built-in XP Mode. But whether schools will upgrade or switch to Windows 7 when it's released in October remains to be seen--especially because XP users must complete a custom, or clean, install if they want to move to the new system.

According to beta testers and Microsoft's web site, switching from XP to Windows 7 will require a "custom install," because there are "no supported upgrade paths." What this means for XP users is that everything on their hard disks must be wiped out to install Windows 7. The disk wipeout will clear all current files and folder organization, as well as all programs and settings.

To save all personal files, users will have to transfer these to an external hard disk first, then resave them after Windows 7 is installed. Users also will have to reinstall all programs and restore all software drivers for printers and other PC add-on hardware--a tedious process that could take hours and is fraught with potential pitfalls.

Also, older PCs (2006 and earlier) probably will not be able to run Windows 7, owing to older drivers and a lack of memory, hard disk space, or graphics power.

This isn't the first time Microsoft has not provided upgrade paths to its latest OS for older software versions. When XP shipped in October 2001, Windows 3.1 and Windows 95 users were left behind. And when Vista shipped in January 2007, XP had multiple upgrade paths, but Windows 2000 and older operating systems did not.

According to Michael Silver, a Gartner analyst who follows Microsoft technologies, it might even be a smart move for Microsoft not to offer an upgrade path for XP.

In an interview with InfoWorld, Silver said it would be risky to offer anything but a custom install, because of all the "viruses, registry errors, and other performance-sapping flaws in the user's Windows environment that would be carried to Windows 7."

Silver's comments echo a statement made by Mike Nash, Microsoft's vice president of Windows product management, in making the business case for Vista nearly a year ago: "Bypassing Vista could have implications for security, support, and regulatory compliance and reduce flexibility in the face of changing business requirements."