MS Wireless Optical Desktop Comfort Edition VS ... 4000

I won a Microsoft Wireless Optical Desktop Comfort Edition last summer. Yesterday, I won a Microsoft Wireless Optical Desktop 4000. Though product names are different, the product pictures on the two packages are the same. I haven't opened the latter one's package yet because I'm going to sell it away. But is there any difference between those two products or Microsoft just changed the name for the product?

I've just visited Microsoft's support site. At the hardware support menu, I couldn't find '.. comfort edtition' so I chose '... 4000'. Then the website required that I enter the product ID. I entered the product ID of '.. comfort edition' and that was accepted. It was weired because when I'd chosen other products, such as '... 1000' and entered the product ID of '..comfort eidtion' it said something like 'This is not a valid ID for this product." Does this means Microsoft consider '...comfort edition' and '... 4000" are the 'same product'?

I just want to know what is different between those two products. Thank you for your answers.