Don't make the classic mistake of going through the slides very quickly - you'll just leave the audience struggling to understand anything at all. Better to trim it down to the important points and make the rest available online for people who want to know more.
I totally agree with this. I'm studying and have to give the occasional presentation. Not being used to this, there have been some important lessons I have learned.
1) Speak S...L...O...W...L...Y. You tend to race through when nervous, and it makes for a BAD presentation. Pace yourself.
2) Practice the presentation first, and time yourself. Do it properly as if you have an audience. Record yourself, if you like. Your 89 slides will take well over an hour to present properly.
3) Under no circumstances should you READ the slides to the audience. Makes for terrible presentations. Slides give a summary. You do the talking. Use the slides as a reminder of what to say, and don't read them to the audience.
4) Don't show-and-tell. Put the whole slide up at once... don't reveal little bits at a time. It's condescending to your audience to only reveal bits at a time.
5) For a 45 minute talk, you need (say) 30 slides maximum. Seriously. You're going to have to significantly trim some of this stuff. Remember, you need to speak slowly! Over a slide per minute doesn't give you much time to say anything about any particular slide... you need to trim the number of slides way down. Like, half to a third. I know you want to put everything in, but fewer slides will make a better presentation! As I said, practice it.
6) OK, now despite the feeling you have that 50 minutes is OK, I'm sure that at the end you're going to have to say "whoops, I'm out of time" and then start skipping slides and really speaking quickly and going through the rest at pace. That makes for a really awful presentation because you're obviously not presenting well. So what you need to do is KNOW how your time is going. And you do that by knowing where you should be (time-wise) on any particular slide. So, you should know (say) that after 20 minutes you should be at slide (say) 40. If you're at slide 30 you know you need to be a bit quicker for the rest. If you're at slide (say) 50, then you can be a bit more expansive about the rest. In other words, have waypoints where you know where you should be, realtive to elapsed time.
7) Although YOU may be happy talking for an hour in a 45 minute presentation, that's rude. People will have come with the expectation your talk will be the advertised time. Keep to it. This also allows time for questions at the end. There's nothing more frustrating than having a way overtime talk where question time is not allowed because the talk took too long.
Anyway, those are my tips. The waypoint one, and speaking slowly, and trimming the number of slides down are the most important.