I hope you don't mind me posting this here( since the program is quite old), but i found a nice application that has done exactly what I needed in regards to what I asked before.:D
It is called TClockEX, and it allows some wonderful customization of the tasktray clock. It has a calendar, which can also be undocked and placed anywhere on the desktop, similar to many of the sidebar gadgets, and that also is customizable. It uses the information you gave from this tutorial/tweak in the same manner.
It can be found here, from the programmer's webpage.
I am running Vista Home Premium and have had absolutely no problem with it. As I mentioned before, I am currently using Windows Classic theme with a few modified colors, fonts, and button/bar sizes and I am able to match my colors with the clock.
It's right click context menu incorporates the default one, with the ability to take you to the system settings menu for date/time. It also has other functionality in regards to CPU monitoring and such. I won't bother with that aspect of it, since I only needed it to display the date/time/ and even a message of indeterminate length ( like your registry tweak above ) in the tasktray when it is at it's slimmest or lowest position horizontally.
Thank you for letting me know this can't be done in Vista automagically through the registry or a hidden setting. It motivated me to find a solution. I was looking at how to do this, and met others looking to do the same and when I found the link to Dale Nurden's wonderful program.
Much love as always
Ron.
p.s. If i have over stepped some bounds by posting this here and the link to his page, please let me know. I will not do it again. :O
always here and telling people about you
R

I was wondering if you knew of a way to display the time + date + year in the notification area, when the taskbar is at its slimmest? What I mean by that is, when the taskbar is unlocked and the vertical adjustment is at its smallest. I am currently using windows classic theme vista home premium, and each vertical increment shows more detail; time, then time and day, then time, day, and date / month / year. I would like to show all and am having a hard time figuring it out. I would like to increase the notification areas horizontal size.
Thanks in advance for any time you spend helping me on this.
Much Love Ronald.

I was unable to display AM/PM on the taskbar. Can u help me out.
But anyway it was worth the browse. MAY GOD ALWAYS BLESS U.