How many search engines can I have on my computer?

I have always used Windows with Explorer until a few months ago when Explorer crashed and I had no disk to reload it. Then I remembered that I had previously downloaded a version of Firefox. So I started using it. And it was a bit strange, because I had used Explorer for so long. So I decided to get experimental and downloaded a version of Safari for Windows. Then I realized I also had a version of that new Google Chrome. I even downloaded Explorer again. (It's a miracle my computer hasn't exploded.) So I just started experimenting with each search engine to decide which one I like the best. Because Explorer had gotten so slow, or at least it seemed like it to me. I really don't want to be stuck without a search engine either, if mine crashes again. What is your advice?

Right now I have: Windows Explorer, Safari for Windows, Google Chrome, and of course, Mozilla Firefox (I think it has Google Chrome built in). But I decided that I like Firefox the best! There are so many great add-ons, and I love the tabs too! But I think that can be my downfall, because it eventually slows my computer down. And I add so many that I find that I have doubled up on many things. But my main question is: HOW MANY SEARCH ENGINES CAN I HAVE ON MY COMPUTER AND IT STILL RUN AT PEAK PERFORMANCE?

Thanks,
Pam B.