Yes I have left my PC running many a time of a night and gone to bed, say for instance to scan for virus's, and no harm has come to the PC. You have got to remember PC's in an office are on 8 hours a day, so PC's will be designed with this in mind.
sype yes I have one of my four on a home network running on BB for more than a week without rebooting keeping my AV ect up to date never had a problem good luck mate PS. some might say cold booting your PC all the time(every day) might cause problems with your hard drive?
If you have household or business insurance, then check to see if there is a clause about leaving electrical goods working but unattended.Some insurance companies are tightening up on things called possible fire hazards.
If you do leave on all night to do some process, it could be worth investing in a UPS (uninterruptible Power Supply, they seemed to have dropped in price like click here I often leave my PC on all day and night when I am downloading
It's the only appliance in our house that's never turned off at night. it's only turned of to reboot when needed. The reason being, I was once told by a repair man that came out to replace a under warranty MoBo that rebooting every day puts stress on the HD and other components (don't know if this is the case or not), be interested in what you find out sype
Further to what spuds wrote, the insurers for my business premises are very strict about what can and cannot be left operational in unattended premises.
I am permitted to have the intrusion alarm, fireproof safety lighting and a FAX machine left switched on. The FAX machine must be in a room equipped with firedoors, automatic power cutoff in the event of failure or fire and an automatic fire extinguisher.
This may seem OTT but I go get nice low insurance rates.