do you use microsoft words? if so tools > word count other than MSW, try http://www.surefiresoftware.com/totalassistant/
I think most word processors have this built in, I know Word and Word Perfect do anyways. If your not using one of them try http://www.wordcounttool.com/
I would recommend you to install and start using a piece of software called XMailWrite. It has many interesting features that will help you in the writing process and optimize your text. This software has Word Count, Sentence Count, Line Count, Paragraph Count, Syllable Count, Average Paragraph Length, Average Sentence Length and Average Syllable Count. The software also enables you to see how many times a word has been used in a text and last but not least it analyzes the text and then grades it according to its readability.