HP Pavillion m733n. Put new graphics card with HDMI port, 1Tb HDD, and dual tv tuner card. Pressing F1 while pressing Power ON causes "entering setup..." to appear but freezes at that point. Took all the cards out and put the original HDD back and it still does the same.
I reset the CMOS jumper and took the battery out as another attempt, but same result every time.
Any other suggestions?

The only thing I can think of is the CPU may be over heating. It freezes trying to boot the OS as well?

The HDD is brand new and unformatted. I don't think it's a heat issue. There's a heat sink fan that's operating. I just replaced the processor which was probably unnecessary.
I'm going to try another HDD that has a working OS installed. I probably won't get back to this project until 11/5. Thanks for the feedback.

try to reset cmos again..make sure the ac is unplugged..remove all your cards and cables..only your mobo, PSU and memory..check if it will successfully enter BIOS..let us know the result