How long does a HDD last?

all of a sudden i started thinking how long does an HDD last? the main reason is that i still own a pentium 4 computer and im using it as a content server for my home network,the computer must be 8/7 years old and the HDD still works so how long should you expect them to work until they die?

well ive abused a 320GB Segate 7200.10 for 4+ Years and it still runs fine, some last long some can fail pretty quick, it can be quite the guessing game.

yeah it does looks like its a guessing game,i have also been abusing a maxtor diamond 250gb 7200 for 4 years and it also works,also i acquired a samsung spinpoint 500gb from my dad's secretary ``brand new`` after she installed a ton of useless stuff on a work computer,the HDD died on me with less than a week i honestly couldnt believe on the lifespan of this HDD

I have a drive from 2003 thats chugging along just fine, its really variable. If i was to give you an average i'd say 4-5 years, so that's that.