Here we go! Found this from an article in PCWorld (Feb 2010). "7 Taskbar Tweaker" :
7 Taskbar Tweaker - RaMMicHaeL's home page
It does other things too, but the only one I'm using is the ability to split the program icons on the taskbar. I work in many different projects that use the same programs (browser, editor, file manager) but in separate instances. I like to separate these instances on my taskbar (vertical on the right) so that they are grouped by projects: Project #1 has 2 browsers, an editor, 2 file managers. Project #2 has 3 browsers, an editor, 2 file managers, etc. In W2k and XP, I used a utility called TaskArrange to let me move them.
When you download it, you'll need a RAR unarchiver, then copy the exe to a new folder in Program Files and launch it. In the options you are given a setting to have it launch (hidden) on bootup so you don't have to copy to a startup folder too.
This program didn't seem to work at first but then I figured it out. Since the default taskbar organization is based on the Application ID, it won't ungroup items that you had open before starting this program (they are all linked to the original ID). Close your programs and then open them again. Each new one that you open gets its own ID now and can be moved around the bar anyway you like.
Only down side is that when you hover your mouse over the taskbar item, you only see one thumbnail instead of thumbnails for all items by that program - which makes sense since they are all different IDs now. I'm willing to live with that as long as I can move my icons around as I see fit again.
7 Taskbar Tweaker :
7 Taskbar Tweaker - RaMMicHaeL's home page