Using OS HDD for storage - Problem, help

So, i have one SSD for OS and one HDD for storage, and it all worked well until i decided to add another HDD. I had an old HDD that i used for OS on another computer but it had plenty of data that i needed and i thought i could just connect it to my new computer, and even though there are two OS HDD inside, i assumed that it will normally boot from SSD, while allowing me to use data from that other HDD. This didn't work and now i can't start my PC, with or without added HDD. I checked all the cables, unplugged and plugged everything back but nothing happened. The fans starts rotating but nothing else happens, except some sort of clicking noise, but it does not seem like it is coming out of HDD. Did i fry something because of another system drive? Anyone have any ideas how can i fix it, and what went wrong?