It’s not quite dead, but now it cannot move as it is stuck in the Martian mud/sand.

The rover landed on Mars in 2004 with a 90 day, 1 kilometre mission. In reality it did something like 10 km over the next 5 years and more (more than 20 times the initial duration). Mostly the extra duration was made possible by some “cleaning” events that periodically wiped dust off the solar arrays that powered the rover. Little green men with wipers perhaps?

What came first Wall-E or Spirit?

Webcomic XKCD's brilliant tribute to Spirit

Read more at Wikipedia and at JPL. The latest attempt is to try and extricate it from the soft soil by driving it backwards, which apparently has its own problems (probably was never designed to do that in the first place).