Can power surge change BIOS of a turned off computer?

I suspect that the power surge may have damaged your CMOS battery which could affect your settings in the CMOS setup. You need a UPS (uninterrupted power source) and I recommend an on-line model. There are many different types and models and the price between and on-line one and a good line interactive UPS is minimal to nothing so you might as well have the best protection possible. A simple surge protector will not protect you from things like a direct hit from lightning. An on-line UPS continuously monitors the AC power and protects you from everyday fluctuations in power. An On-Line UPS with a +/-2% output voltage regulation will protect you from all different types of power problems including, brown-outs, surges and other things. If the power goes out, it immediately switches to DC power and runs on the battery with no interruption in computer usage. You can choose to save what you are working on and shut down the computer or keep working for up to 4 or 5 hours with the On-Line model. Off-line UPS models give you around 20 minutes to save everything and shut down your equipment. You may not think that you need this type of protection for a home computer but one large surge in power such as a lightning strike can fry all of your stuff and continuous everyday power fluctuations can have bad long-term effects on your equipment too. I have provided a link below that will tell you about the different types of UPS models and it even has a tutorial provided to walk you through the details. Back to your original question I think that your hardware was damaged, probably your CMOS battery and yes to answer your question, buy an uninterpretable power supply. Make sure that it has enough ports to put everything through it, computers, printers, monitor and I know they used to come with a phone line input so if you have DSL make sure it has an input for that or if you have cable or satellite internet make sure there are inputs for that too. Hope this helps.