I am not saying you need to, but just for general information, if you use the Windows Anytime Upgrade to go from Home Premium to Professional, there is no reinstall of software. All the features of Professional and even Ultimate are in the OS, they are simply activated and settings applied - it takes about 10-15 minutes once you buy the anytime upgrade license.
But you should not even consider upgrading in order to use Virtual PC - XP mode without first checking that your computer meets the needed specifications for VirtualPC.
If, in fact, there is only one program you can no longer run, I would suggest a search for "freeware calendar program"s, check the features to see that they meet your needs, and try some of those, or as a last resort go to the store and buy one. You should let the salesperson know how you use it ... are you importing your own pictures and printing calendars? does it notify you that you have an appointment? Your old 16bit wouldn't but some of the newer versions may even be able to sync your schedule with an iphone etc (this may be more than you want). The point is, be clear on the functions you want, need, or may be of interest. It would definitely be cheaper to buy a new program than to pay the guru to upgrade your OS to get antiquated software working - anyway, many times you pay for guru and really get Joe the Plumbers helper.
It can be frustrating learning a new Operating system and new programs but there is that feeling of accomplishment when you master it ... or that sense of relief when you drop the whole dam* thing off a roof
