Q:

Downtempo song, where a female voice says “Don't stop”

The song is very relaxed and I am reasonably confident that it features smooth-sounding (closer to sine wave than to the saw wave) synthesizers. I recreated the main theme here. I recall the main theme follows immediately after the female voice.
With regards to the helpful tips from “What should I do to improve my identification question?” suggested by Bebs:

I attempted to search for the the lyrics “Don't stop” at Lyrics Wikia, Metrolyrics, Lyrics Mania, and Find Music By Lyrics with no success. Admittedly, a single soundbite makes for a poor query.
The song was used as a background track in a YouTube video I listened to around 2010. The year of production is unknown to me, although this one may become clearer if we pin down the genre.

A:

You might be thinking of "Don't Stop" by ATB, with it's very distinctive sliding notes sound.
youtube ATB Don't Stop official video

