TextAloud "reads" text using a computer-generated voice. No, I am not suggesting you have your presentation narrated by a computer-generated voice. But you can let this voice read your script and help you hear where it needs to be modified to sound more natural.
I usually read a script aloud four or five times before I am satisfied it is "real." When I let TextAloud read it, I can "hear" it more clearly.
Text you paste into the TextAloud window is read by a synthetic male or female voice.

You can also save the voice file as a WAV, WMA, or MP3 file. TextAloud also reads any selected text in any program that supports the Windows Clipboard.
Text-to-speech technology is not perfect. In a sample I pasted into TextAloud, the word "read" was pronounced in its past tense when it should have been its present tense.
A basic pronunciation editor lets you correct a problem like this by assigning one of the tenses a unique string of letters and specifying this string is to be pronounced as it should be for that tense of the word.
If your text contains technical words, jargon, slang or other words TextAloud is unable to pronounce, you can use the advanced editor to string together English phonemes that result in correct pronunciation of the unrecognized words.
You will find other uses for TextAloud, too. More natural voices are available from a variety of vendors, but none can replace a real human voice for professional narration quality.
TextAloud only works on Windows (98 or later), but the MP3 files it creates can be listened to on any computer, even an iPod.
NextUp recommends 64 megs of RAM and 10 megs of disk space, but in my experience, you need as much RAM and disk space as you can get to have success with any text-to-speech tool.
Download a trial copy or watch a demonstration. at NextUp.com.
TextAloud is $29.95 U.S., a very good price if a simple text reader is what you need.