I have a Samsung PS43E450 TV (pic here). I lost the power cord. Can I just use the power cable from my PC (since it fits in the slot), or will it blow up?
Yes, no problem. That's the same connector.
There could be issues if you bought the TV in a country with different mains voltage. You'd have to check with the manual/label on the back if it works with the voltage of your current country then.
That's a common IEC-60320 C13 socket. Any cable with a c14 plug at one end, and your local outlet type at the other will work. These are standard off the shelf cables.