If you're going to be away from the computer for more than 1 or 2 hours then shut it down. The problems of heat expansion/contraction the computers had during the early 90s have been mostly eliminated and you just end up wasting electricity.

I never shut mine down, it's only off when lightening strikes, and blows the power supply fan 

I turn mine on when i get up in the morning and turn it off when i goto bed.....

It put's less stress on the comp cos you only start up and shut down once a day......

Been doing it like that for years.

Mine's on pretty much 24/7...

Well turning it off guarantees no virus hehe

It probably comes from the virus loading itself into the os on reboot with systemfiles....

An IT told me, that it's actually not good to keep turning it off, and that he never does it hehe

I hardly ever turn my computer off, and certainly not to go to bed everyday.  Besides, as most large applicances having power saving features, the use of power is pretty negligible.  I dare say the regular use of your washing machine, and/or dishwasher would use more power than the constant use of your PC.

PCs (i.e. their componentry) are designed to run for long periods of time without needing to be shut down.  Powering a unit on and off everyday would cause more stress and wear on the moving parts than keeping them on all the time.  Which is common sense really.

Haven't shut mine down in 17 years

* BS disclaimer *

Yep DIGI, that's basically what that IT told me too

There are so many moving parts.. Keep in mind that current hard drives have to spin up even if the computers is on already if it's been unattended.

Few IT guys are also materials engineers.

As far as elecrical use......

http://www.switched.com/2007/10/31/five-percent-of-u-s-electricity-wasted-by-vampire-electronics/

Lantec, the guy at the PC shop even told me that hehe

So ...I'd ask myself.......how does he make money.......

By selling me POS computers

24-7 carbon footprint

http://www.yorkblog.com/greenmesh/2007/11/1-computer-running-90-days-1-b.html

Crikey... now I feel bad.. it's just that.. IF I turn it off.. it might never boot up again

I don't have time to turn my PC off.  Doing dream rendering requires me to have my PC on 24/7 and it's running 100% almost all the time. 

It's a quad core overclocked to 4ghz and if I close the office door it can get up to 80F overnight in the office.

Only time I turn mine off is to clean the dust from the fans and case as such is needed once a month for me.

Then and only if I need to remove a device or hardware which can not be removed via remove hardware cmd.

Most hard drives today are made to stay running all the time. Not saying it is not good to turn them off. Being I have an external Western Digital Book which if I am not using it... I remove it and shut it down till needed. Sort of just sits there on the bookshelf till I want to take it down and use it for whatever reason.

But for the most part... I have an Old Sony Desktop I've had for almost 5 years now and it stays on constantly unless it is turned off for reasons stated earlier.

Otherwise I feel that turning them off and on does shorten the life span due to startup of hardware and surges of electricity at those given times. Most damages to computers come from dirt and heat!

Leave it on !!!   Keep it CLEAN !!! and  RUN IT COOL as possible !!!

Results are you have a ready system running well.

You mean you can turn a computer off?

I have all of my PCs running 24/7 and it helps heat my home which allows me to run my heater less. One carbon footprint trade off for another.

I shut mine down every night, in case there is a power outage which we do have on occasion.   But if the weather looks good, and I need some rendering done, it stays on till it is finished then it shuts down automatically.

It really is just a matter of personal preference. Mine stays on for days sometimes. Sometimes it goes off every night, depends on how I feel, whether I'm downloading something big, etc.