Conversation so far:
What happened on January 21, 2004?
On January 21, 2004 (sol 17), Spirit abruptly ceased communicating with mission control.
What was the problem that caused the Spirit rover to stop communicating?
The craft was in a fault mode.
Was the problem with the rover Spirit a software or memory issue?
The problem was with Spirit's flash memory and the software that wrote to it.
How did engineers try to solve the problem with the Spirit?
The designers had made it so that the rover could be booted without ever touching the flash memory.
What did the team do next to fix the rover Spirit?
NASA engineers came to the conclusion that there were too many files on the file system.

Question: How did they get rid of the extra files?
Self-contained rewrite: How did the engineers get rid of the extra files on The Spirit?