Windows XP taskbar address tool

I just recently put the line run command aka the address bar on my taskbar so that I could clear off some of my quick launch icons. Commands i typed in the address bar like: winword, excel.exe, etc worked fine, but when I typed in mspub.exe from an old Office 97 copy of Publisher, I got an IE icon and sent to an unavailable website via the IE browser. Same thing happens with BearShare.exe. Does anyone know why it does this with only certain software executables?

Thanks, StratMan23