I can't quite convince myself that this is necessarily a serious question, but assuming it is....
There are a number of contributors to infertility. One is genetic - some people just aren't as fertile as others, all other things being equal. Clearly, the laptop won't affect this.
The second is environmental - chemicals in the environment and diet which reduce sperm counts. Again, unless you eat it, the laptop won't affect this either.
Third is frequency of ejaculation. Do it too seldom, and the little guys get old and less mobile. If you spend so much time with the computer that you never... release, well, the laptop might be a factor. Do it too often, and there aren't enough of the little guys produced to keep up, as it were, so, if you spend a lot of time visiting non-family-friendly (ah, a deeper meaning to that phrase now) sites, then, again, the laptop might cause problems.
The final factor is the general temperature of the testicles. If you use the laptop on your lap without any padding and with it directly on your crotch, then, yes, it can definitely reduce fertility. Unless you live in arctic conditions, in which case it might just keep the little guys from freezing.