That's impressive. I suspect a couple of mine are pushing the 5-6 year mark. They've been moved around a lot, transplanted, run in a hot room, probably all the things you shouldn't do, yet still running... I think I might go pull out some stats

Here we go. Just under 8.5 years for my oldest one.

Ive got a 120MB SCSI drive from my Amiga days that still works. 

Drives in my home server are getting on.....

Power On Time  . . . . . . . . . . . . . . . . . : 845 days, 23 hours
Power On Time  . . . . . . . . . . . . . . . . . : 1517 days, 6 hours
Power On Time  . . . . . . . . . . . . . . . . . : 1209 days, 18 hours
Power On Time  . . . . . . . . . . . . . . . . . : 528 days, 12 hours
Power On Time  . . . . . . . . . . . . . . . . . : 2502 days, 14 hours
Power On Time  . . . . . . . . . . . . . . . . . : 2718 days, 7 hours

Last year I had my ancient OS/2 box motherboard die.  So I transferred all the data off its IBM Ultrastar 9LZXLW 10000 rpm 9 gigabyte SCSI drive and set up OS/2 running as a virtual machine.  Then a few days ago I was sorting my ancient emails and ran across one where I posted the benchmarks for that drive shortly after I got it in May 2001.  So that drive had been in pretty much 24x7 operation since then until early last year - around 16 years.  Most the rest of that PC had been replaced along the way (including the motherboard), but that drive and the Adaptec SCSI card it was attached to just kept on going.

if its 640Gb, it really isnt that old
Got a few 80Gb's here

old is such a relative term .A 'PC Direct' PC still in use (running 24/7), now thats old
:-)

My first HDD was a 20MB Western Digial XT drive in my A590 for my Amiga.....  that soon got replaced by a 120MB SCSI (the one mentioned above) - then the A590 got replaced by a GVP A530 unit and a GuruROM - ah they were the days ;) Anyway getting off topic now LOL....

My first HD, in my 1st PC was a MFM 10Mb

A huge thing , that would get the whole PC moving (literally) :-)

Remember the Bigfoot drives , so popular, yet so awefull .