You can perfectly go through the city without being hit by a car. Leaving the house doesn't imply death.
-Tuxman
Of course! But you can also install software on your computer without polluting your registry. This is an English language thing, I think. There is a saying in English that if you want to avoid the negative consequences of some action you should simply avoid that action altogether. For example, if you don't want to die in a plane crash, don't fly! To make some other examples: if you want to avoid slipping and hurting yourself in the shower, don't shower! Don't want to choke on a chicken bone? Don't eat chicken. Scared about a paper cut? Avoid paper.
I suppose, really, I read your comment in haste and interpreted it in light of the English saying described above. So I read it like this: ANYTHING we do on a Windows computer is going to affect, and potentially pollute, the registry. Therefore, if you want to avoid polluting your registry you shouldn't install any software on your computer. Now I realize that you probably meant it in the way that I rephrased it: just be careful about what you install on your system.
EDIT: corrected some atrocious grammatical errors introduced in my last edit!