It's always a good idea to have a visual aid to accompany a sales presentation. But note the term: "Visual aid." Your slide deck should support your speech, not compete with or detract from it.
Is your visual aid more like a visual hindrance? This SlideShare from Deck Rooster can help you spot the flaws in your deck before you show it to a prospect.
For instance, how many ideas are you communicating on each slide? If you're cramming three or four ideas on a single slide, your message might get muddled. What about the file name of the presentation? Is it saved under a title that makes it easy for you to search for it, or your client?
Run through this checklist before you share your sales pitch deck with a prospect, either during a live presentation or over email. There's nothing quite like a beautiful visual aid to brighten up a presentation ... and nothing quite like an eyesore to call your credibility into question.