Perhaps the best and most useful translating software is the Babylon dictionary.
It is the most powerful single click desktop translating software.
The feature of Babylon is its patented OCR Technology that works in any Windows program, such as Word, Outlook, Excel, Internet Explorer and Adobe Reader (PDF documents).
Babylon should be the best and professional English to English dictionary, but also for many other languages. The data mining technology and big users base make their vocabulary database always up-to-date. Babylon Ltd. has also partnered with publishers of dictionaries and encyclopedias, such as Oxford University Press, Merriam-Webster, Encyclopædia Britannica, Larousse, Langenscheidt, Van Dale, Melhoramentos, and Taishukan.
Since 2006 Babylon provides access to a static version of Wikipedia in thirteen language versions. Now you could have your wiki in your desktop.
The price of Babylon varies as diferent version, it cost 80 until 100 Dollars. For professionals and scholars, Babylon is a tool that one must have.
For more information, about Babylon Dictionary, just click this here.
OK, well the best is not always the fittest. People have to buy this software to get the full function, but there are still some freeware to meet the basic application.
The most distinguish software is Lingoes.
Official website is
http://www.lingoes.net/
This is their introduction in the official site.
Lingoes is an easy and intuitive dictionary and text translation software, It offers lookup dictionaries, full text translation, capture word on screen, translate selected text and pronunciation of words in over 80 languages. These language are English, French, German, Italian, Spanish, Portuguese, Russian, Greek, Swedish, Turkish, Chinese, Japanese, Korean, Polish, Arabic, Hebrew, Vietnamese, Thai and more…
This dictionary is also very powerful and support single click function, it support websites and PDF. At least the English-English translating is quite good.
My favourite version is the green portable edition.
This is green portable version of Lingoes released by Lingoes Project. It’s discreet and portable without installation. You can unzip it into USB Flash Drive and run it anywhere. It’s the best choice to use in cybercafe, school, library ect. Specifically for mini size PC & laptop, e.g. EeePC.
The download link is here.
Dont forget to mention, if people dont need the single click function, google offers very excellent translating tools online.
If you need a Chinese English desktop translating software, you could get a very good one online without spending money.
Step 1. www.pack.google.com, this is a collection of free software collected by Google.
Step2. Choose the Chinese option in the listing

Step 3. Then you find this one 谷歌金山词霸合作版
