How can people use IE?

This is a rant.
How can Microsoft possibly market a browser as ABYSMAL as Internet Explorer? Aside from stomping on standards left and right, and putting out plain old BROKEN implementations, ths browser is a menace to every system.
I have to run it on the Win2k box to test things I’m running for a client. On that w2k box, I normally just use my Firefox installation. Anyway, running up IE, and I -immediately- get a pop-under advertisement.
I have run IE perhaps 5 times since I set this machine up.
Microsoft, you’ve built a product that is unuseable without third party tools (such as Spybot and Ad-Aware) that fix the faults in your product. Sheesh.