Is it bad to leave a PC on all the time?

I think computers are really designed to be kept on a lot of the time. However I do turn mine off at night as it saves on my electricity bill and is better for the environment.

It doesn't harm your PC to leave it switched on all day and night. I work in the IT industry and the IT geeks I work with (I'm not being mean, I'm nearly a geek myself too) tell me it does no harm to leave computers on. In fact, they say every time you switch your PC off and back on again it reduces its life more than if you leave it switched on. We leave the backups scheduled overnight and the antivirus update runs in the background all the time - no point waiting till night-time to run that, viruses don't wait for updates before they attempt to spread! Hope this is useful to you :)