CMOS Bios Password problem

Hi, this might be a tough subject so i apologise for any information i get wrong.

I have an Intel DQ77CP motherboard pre-installed in my gaming PC which has been working fine until a week after buying it.

I came across a CMOS Checksum error every time I started it up and so I bought replacement motherboard batteries. Now I’ve done that, I receive an Intrusion Error which leads me to the BIOS password entry. Originally the password for the BIOS was literally just pressing enter with nothing in the box, now it’s not, and I have no possible way to get into my PC.

I would like to find out 2 things:

1. How to get back into my PC with everything working functionally and
2. How to prevent the BIOS password entry from appearing everytime I boot up.

Thank you in advance