LingoPad is a free offline dictionary for Windows.

LingoPad contains a German English dictionary; other dictionaries (Spanish, Italian, French, Japanese, Chinese, Turkish, Kurdish, Norwegian or Arabic) can be downloaded as well. You can also import your own wordlists and use them parallel to the existing dictionaries. For each dictionary, a user dictionary can be defined to include additional wordlists.

The program is freeware and can be downloaded and used free of charge.

Features
German English dictionaries
further dictionaries (e.g. Spanish, French, Japanese, Chinese, Turkish, Kurdish, Norwegian) available on clicking Online update in the Dictionaries menu
import of own dictionaries possible (Unicode ready)
freely definable user dictionaries
wordlist editor
search for beginning, ending and middle part of a word (*ending or *middle*)
search for collocations
activation possible with a customizable HotKey - automatic search for a tagged word or word from the clipboard
list of latest search words
download on memory stick possible
offline use
phonetic transcription for many English words
user interface in German and English
direct links to look up words on Wikipedia and various search engines