By Fred Langa Looking for a sure-fire way to keep your oldest Windows applications alive while living in a Windows 7 world? You’ll find it with Win7’s XP Mode, a free and fully functional version of XP Professional SP3 that runs entirely inside Windows 7. And even if you don’t have ancient apps to support, you gotta admit: keeping XP around for those times you want to indulgein a bit of nostalgia is pretty cool.

XP Mode is a free add-on for Windows 7 Professional, Ultimate, and Enterprise — Win7 Home Premium and Starter don’t qualify. For those versions, or in any case where Microsoft’s XP Mode doesn’t work, there are other alternatives I’ll discuss at the end of this article.

Windows 7’s XP Mode runs within a virtual PC (VPC). It’s not a dual-boot setup, which lets you run only one OS at a time; a VPC lets you run a second operating system within your current OS, giving you access to both simultaneously.

In a VPC, all the hardware (video boards, hard-drive controllers, etc.) an OS needs is emulated or moderated by the VPC’s software. In Win7’s XP Mode, the virtual hardware boots and runs XP Pro SP3 within a Win7 window (see Figures 1 and 2). It’s sort of like having a second monitor, but on your Win7 desktop.