To add to bochane's suggestion, you should also remove
ALL RAM sticks in addition to the video card, DVD player, and
ALL hard disks including any usb external hard drives or flash drives. If you don't get any audible
BEEP CODES, then your Motherboard has failed and must be replaced!!
It is the cause of your system no longer booting when cold. This of course would be simple to do if you have a self-built PC or what we call a Custom-rig or Gaming-rig. If you bought your PC already assembled, we call this an OEM PC (
Dell, HP, ACER/GATEWAY, etc.), you just have to figure out how to take it apart. If you've never done this before, I suggest you go the manufacturer's website and download the free user manual. This will be in
PDF format most likely so you will need to have a working computer (perhaps another computer in your home or laptop or borrow from a friend), and it will show you how to disconnect or change the above components, and most importantly how to open up your PC case.
Since you replaced your
PSU (Power Supply) and your
BIOS battery; you've replaced the obvious components that can cause this type of problem; and now you are down to the very expensive proposition of having to replace the Motherboard or replace the entire computer.
Lastly, if your computer came with Windows7, and that's likely since you are posting here in the Windows7 Hardware forum, it's probably 5 years old or older, but if you bought the computer refurbished, some of the refurb outfits like Joy Systems, Inc. will offer up to a 3 year factory warranty on their PCs.
It might be worth a phone call or E-mail to them to see if this is the case. I've seen them replace faulty Motherboards on their PCs for customers if their PCs have been purchased within their warranty period for free!
The rub their is that most of the refurb PCs you buy on the Internet or at retail computer shops like Micro Center, only come with a 1 yr. warranty standard, the 3 year warranty is sold either at checkout on the web or by a salesperson at the store, and you have to pay extra for that; usually 10% of the purchase price. So, a 3 year warranty on a $200 computer for example might have been about $60-$100 or so. If you remember doing that, and have the receipt or warranty paperwork, you can contact them and they will help you out with a new Motherboard as explained above.
Best of Luck to you,
<<<BIGBEARJEDI>>>