Consider this. Could you give your presentation without your slides? A number of years ago, my company was offering a series of seminars on calibration (this was when ISO certification was the big hot topic). I had given the presentation dozens of times, and I had an important client who wanted me to make the presentation to his team and some senior managers. I may be dating myself when I tell you that this was in the days when you had to print your presentation on overhead transparencies. As fate would have it, the bulb on the overhead projector blew after the first few slides, and when I dug out the spare bulb, it was also blown. What could I do? I knew the presentation by heart, so I went ahead and gave it, using a flip chart and marker when a diagram or calculation was needed.
At the end of the presentation, several of the managers approached me and told me it was one of the best presentations that had ever seen. Personally, I don't think that it was all that great, but I think the fact that I pressed on in spite of my failed technology added to their opinion. I actually liked the part of the presentation where I did the calculations on the flip chart, so I pulled the math slides out of my slide set and brought a flip chart for subsequent presentations.
What I learned by accident that day is something that all of todays presentation gurus teach. Use your slides to enhance your presentation. Use simple graphics. Know your material inside-out and backwards. Be prepared for any contingency.
Good luck with your next presentation!