Can I leave my compaq Presario on over night plugged in without it messing up?

Yes, but it's not a good idea to do it all the time.

If you get lightning strikes and it's on AC (for laptops), it could fry.

Also, if a fan dies, it could overheat, and it will needlessly collect dust.

Not to mention the running costs.


Once in a while is OK if you need to.

what if I have a surge protecor?

Surge protectors aren't perfect, and don't protect against overheating.

It's OK to leave your PC on every now and then if need-be, but you're better off shutting down when possible.