Windows Vista, like other versions of Windows before it, automatically creates a boot menu that lets you choose between launching Vista and your previous version of Windows each time your computer starts. All you have to do is create a new NTFS partition on your hard drive and install Vista as a new installation to that partition.

The setup routines of some previous versions of Windows, including Windows XP, have been able to create new partitions as part of the Windows installation process. The betas of Vista display this functionality, but it's grayed out. I recommend the use of a third-party utility called PartitionMagic.

I've been an active PartitionMagic user for over a decade. PartitionMagic, developed by PowerQuest, was the first nondestructive, dynamic partitioning utility. What that means is that you can install PartitionMagic on any Windows computer and use it to create a new partition on your hard drive from the unused storage capacity on the drive. PartitionMagic will shrink your existing partition to a size you specify, create a new partition, assign it a drive letter and format the new partition. And it will do all that without harming any of the data in your original partition. PartitionMagic, which Symantec purchased a few years ago, supports Fat32, NTFS and a wide range of other file systems. There are many other disk-partitioning utilities that perform the same functions, and even a few that are free. I haven't tried them all, though. (I have used and like Paragon Software's Partition Manager.) For a list of other partitioning products, see this Wikipedia entry on disk partitioning (http://en.wikipedia.org/wiki/Partition_(computing)#List_of_partition_utilities).

To install Vista smartly in a new partition, you need at least 20GB of free storage capacity. Create a new 15GB drive, and leave a minimum of 5GB free to your existing Windows installation. That will leave you a bit of room to install apps on your Vista partition. This configuration is fine for a temporary installation of Vista just to see what it's like. When you're done, delete the Vista partition and restore things as they were.

If you plan to make this a long-term Vista installation and you're planning to move data over and install Office 2007 there, make it a 20GB or 25GB Vista partition. You also don't want to choke off the operating system in your main volume or your ability to add new apps and data there. So leave at least 10GB free, and 15GB would be better. If you don't have 20GB to 40GB of hard disk space free, upgrade your drive capacity, clean install Vista on a different machine (wiping the drive) or use the virtual memory solution I detail later in this article.