The numerous and confusing differences among Vista versions have led many people to opt for Home Premium rather than the full-featured Ultimate. But you can give Home Premium many Ultimate features, often for free.
Make image backups
The backup program built into Vista Ultimate lets you make images that exactly duplicate a disk or partition, byte for byte. Through it you can easily restore a failed disk with the operating system, files, and settings running as they did before the crash. You can add this feature to Home Premium by shelling out for Symantec's Norton Save & Restore or Acronis's True Image. If you have a Seagate or Maxtor hard drive, you can download free versions of DiscWizard and MaxBlast--imaging utilities that are based on Acronis True Image. An unpolished-but-free alternative is DriveImage XML from Runtime Software.
Vista Ultimate's Shadow Copy automatically backs up different versions of the files you save, so you can easily revert to one of them. To get the same protection in Vista Home Premium, look no further than the freeware utility FileHamster from Mogware. Each time you save a file, FileHamster prompts you to add a comment to annotate that version and (optionally) to protect it from deletion.
Build a virtual machine
Through Virtual PC (downloadable), you can run other operating systems as if they were applications within Vista Ultimate. This is useful when you need a program that can't run in your current version of Windows, or when you want to browse safely.
VMware's free VMware Player brings this feature to Home Premium. After you download and install it, you must go back to the VMware site to download one or more "virtual appliances" that run in VMware Player (many of which are free). For example, I downloaded "DSL," or Damn Small Linux, complete with desktop utilities.