The consumer versions of Vista go on sale Tuesday, January 30th. If you're thinking of upgrading a Windows XP machine to Vista, you first need to find out what if any Vista editions will work on your machine. Then you need to select the version and decide how to install it. That last issue is more complicated than it might seem because there are three different ways to install Vista on an XP machine.
The easiest way to see if your machine is compatible is to go to www.microsoft.com/windowsvista/getready and download a free program that will scan your system and tell you what, if anything, you need to do to make your machine Vista ready. Make sure all of your peripheral devices are plugged in because it checks to see if Vista is compatible with those devices. If your graphics card isn't up to speed or you don't have quite enough system memory it may tell you that you can run the $99 Home Basic edition but not the $159 Home Premium version that gives you some of the cooler features like translucent windows, DVD movie burning and Windows Media Center.
If your machine can't run Premium, you might be able to make it compatible by getting a new graphics adapter and upgrading to at least a gigabyte of system memory. I replaced my old video card with an nVidia GeForce 7600 (about $170) and am getting great performance.
Also, check with the developer or manufacturer of any hardware or software that you can't live without. You want to make sure your mission critical products are Vista compatible before upgrading the machine. If not, find out when and if an upgrade software or driver will become available and wait until then. Finally, gather all of your program CDs so you can re-install your software if necessary. Don't make the mistake of installing Vista and later discovering that I you have an install CD for a program you'll need.