Windows 7: Is leaving your computer on all the time (24/7) better for hard drive?

So put numbers to it. Power cycling a drive 10 times a day for every day (including holidays) means the drive fails maybe ... 27 years later. So yes, it will fail sooner. Otherwise the drive might last 230 years. Nobody cares. A failure after 27 years or 230 years is no failure due to power cycling.

A useful answer includes perspective. That means numbers. Power cycling was destructive only when subjective claims (junk science) were considered. There never was a controversy about power cycling. There was, unfortunately, too many consumers who give credibility to hearsay. Subjective claims. Answers based only in wild speculation or observation. Those answers are quickly identified and disposed. No numbers means little credibility.

I'm layed back and simple. Years ago when hard drives clanged and banged doing their/there job to a degree their/there was a concern with all the charts and grafts and how you used your hard drive. I don't believe that todays hard drives have that concern. Use your system as you see fit. If the hard drive fail it will not be because of the way your use it. Hard drive life span is controlled by the quality and standards it was made by.

I think the numbers are not relevant unless you save every drive from every machine you ever owned. For the average user who puts the PC to the curb when it's too slow to use anymore, it doesn't matter. The machine becomes obsolete before the HW fails unless you're so unlucky you got a dud component that escaped QC testing.

Seems like this argument is obsolete too, to be honest.

This sums up what I believe to be the answer to the question at hand. Short of dropping it, submerging it in water, or scooting your feet across the carpet and zapping it, nothing you do to a HDD will be cause for concern. If it is bricked when you get it, it slipped through quality checks. If it works for a week and then dies, there was a manufacturing issue. If it runs for 20 years and then locks up, get over it. Just run one however you see fit, that's what they are built for.

Server/Enterprise grade HDD's are designed from the ground up to run 24/7, 365 days a year with as few interruptions as possible. They are more expensive though, and occasionally they do send one out that is bricked, or one that goes bad in a week. Nothing is immune to Murphy's Law.

Yeah, Interesting topic. For me, my computer is turned off for about 5 hours a day, to save electricity costs when I'm not using it.
(Yeah, I'm Scrooge McDuck :P)

Nobody know what toll cycling takes on a HD.
The general view I've seen by those I trust is that heat cycling is not good for electronic components. But that doesn't stop PC's that are turned off and on for years from running flawlessly for years.
I turn off lights when I won't be in a room for a while too.
Why waste power? You can get an estimate of power use for your PC, but 60-200 watts is typical. Even at idle most cpu's use 60 watts or so.
So would you leave a 60 watt bulb on for days at a time?
If yes, then leave your PC on.
I turn mine off if I know I won't be using it for a couple hours.
And I never leave the house with it running.
Power supplies sometimes fail, and shoot flames. Never happened to me, but I've read of it happening more than once when looking at PS reviews.
Best to keep papers and other flammable stuff away from the PC if you're leaving it running unattended.
I'd rather turn off the PC than rearrange my desk.

I actually saw some home servers that were run by less-than-optimal admins and some of the bunch were so full of dust that did actually catch fire and burn a bit. They managed to melt themselves and little more (they were in the basement of a brick house), but was pretty fun to arrive at the "disaster scene" with all that smoke to see if there was something left to save in their HDDs.

But that was an obvious human error, professional server farms don't have the habit of burning down every once in a while even if they run 24/7.

I leave mine on 24/7.

As long there is no bumps in the CPU while the hard disk is working,better hard disk cooling,etc there is nothing to worry about leaving your PC on for 24/7.

I sincerely hope you are joking with this comment. If not, I'm not entirely sure what to say. HDDs are mechanical parts, and the more wear and tear you put on them, the more you increase their chances of failure. Start your car several times a day, and you will increase your chances of a failure there, too. Common sense, basic principles. The numbers you are choosing to throw around are outlandish, at best, suiting only to make an argument where there is none.