I am occasionally asked “is it OK to leave my computer on overnight?” or “can I leave my computer on all the time?”
My answer is a resounding “yes, I do.” My desktop, my wife’s desktop, my Linux box and my Home Theater PC (www.terryshometheater.com/htpc) all run 24 hours per day, 7 days a week — 24/7.
My notebook does not and should not — the issue with a notebook is that the LCD screen’s light sources will dim and wear out. If you have an LCD screen for your desktop, be sure to use a screensaver and the power-saving option to “turn off monitor after ___ minutes of non-use.”
If you choose to let your desktop computer run 24/7, be sure to have it on an uninterruptable power supply (UPS), preferably one that is 600 to 1000 VA. Most come with a USB cable and software to run on the PC to monitor the status of the UPS and the power _to_ the UPS.
If your power goes out, the software detects that change (via the USB cable from the UPS to the computer) and triggers a safe shutdown of your computer.
If you have an LCD monitor, be sure to use a screen saver and the Windows power-saving functions to turn off the monitor when it is not in use. The light sources for an LCD monitor are several small fluorescing tubes — they will dim and eventually burn out. Even if you use a screen saver, you should have the screen power-off after not more than an hour of non-use. This will protect the monitor’s life.
I do not believe that LCD monitors suffer that fate that CRT monitors do. CRT’s have been known to burn an unmoving display into the phosphor of the tube. That problem was more common in the old monochrome monitor (green/black) days. But, I wouldn’t want to try to burn a 19″ monitor to see if I could do it.
Similarly, my 52″ rear-projection television’s instructions said not to leave static images on the screen (from game consoles or unchanging displays from my Windows-based home theater pc) to prevent burn-in of the screen.