While it is common knowledge that Microsoft, ah, ahem, borrowed ideas from Apple, it's not so widely known that other companies came in for this treatment too.
Interestingly, Acorn's RISC OS operating system had a concept similar (though more consistent in operation) to the Windows Taskbar. Storage devices, filesystems and printers loaded on the left of the icon bar, while applications loaded on the right hand side. When they met in the middle, the icon bar would scroll as appropriate.
Other Acorn concepts nabbed by other OS vendors include installable filesystems, the system tray, image filesystems, a modular kernel, and of course the big one- desktop RISC workstations.
Apple and Acorn were, for a short time, in collusion to produce CHRP-based systems. The only one that actually came to light was the Acorn SchoolServer, a rebadged IBM RS6000 system running Windows NT 3.5.
Performance was very poor indeed and didn't sell well. Acorn (well, ARM anyway) had been in cahoots with Apple for some time, having supplied the ARM6 processor for the Newton.
It's also known that Microsoft bought several RISC OS based machines from Acorn in circa 1993. What happened to them is somewhat uncertain...