3½" PATA Western Digital Caviar SE (250MB) makes steady ticking sound when idle
First, make sure you have backups of the drive content (advice is good regardless of noises).
Having experienced similar "ticking" noises before, I believe one of 2 things are happening:
- Your drive is dying (how old is it, BTW? You mentioned PATA, so I assume several years - in which case it's not a surprise).
- Your drive/system is over-heating. Look at the temperatures of your system.
Even if it is scenario 2, IMHO your drive's days are numbered - refer to advice at top of reply.
Good luck!