Windows 3.0 contained three kernels
 

"The 16-bit Windows kernel was actually three kernels. One if you were using an 8086 processor, another if you were using an 80286 processor, and a third if you were using an 80386 processor. The 8086 kernel was a completely separate beast, but the 80286 and 80386 kernels shared a lot of code in common." As always, Raymond Chen delivers. If you don't yet follow his blog, you should.

http://osnews.com/story/26774/Window..._three_kernels