I am reporting these incorrect answers more frequently now. Their english translations are mechanical and unreal to any native speaker. My translation is as follows: the watch has almost stopped. In this case, the state of being 'is' s/b replaced with the possessive 'to have'.
Parado could've been used if the English was The clock has almost stopped... In the same way it'd feel a little weird saying The clock is almost stopped, even though it's correct.
Both sentences have the same meaning, but you have to be careful about translating literally and translating something else.
As for what we normally use, at least in Brazil we say O relógio está parando (The clock is stopping) C: