If I change the startup screen, what happens to the old startup screen?

Acer Iconia Tab A500 mfg. 2011, now 11 year old.
the battery is now end of life, called BAD
replace it.
11 year old batteries are no good now.

You have made the same mistake that I and many others have made before you....making too many changes at one time. It makes it difficult, if not impossible, to know which, if any of the changes is the problem. That being said, I'll try to help. First, did you reposition the BIOS DIP back to the proper position? Otherwise, the BIOS is held in reset and cannot work. I would, for now remove the new video card and re-attempt using the onboard video. This removes one potential problem. Try that and see what happens.

you bought a fake battery or the battery terminal are bad and are having poor contact with the battery.remove the battery and try to clean the three golden panels that come in contact with the battery

Change CMOS Battery

If the problem started after changing your graphics driver, then reinstall the old driver. Acer should have the original drivers on their web site. If you don't want to go back, you could try updating the bios, that also should be on the web site.

That usully happens when there is a USB stick in on startup.
This happened to my when I forgot to remove my old iPod nano from my PC

mostly this problem occurs in dv series.
the problem is in the builtin vga card of the laptop.
contact hardware vendor for its repair

Hi!
Your old Rage Pro is an AGP 2x, where the Nvidia is an AGP 8x.

The Nvidia is probably not compatible with your motherboard.

Also, I think Nvidia needs much more than 320 Mb ram.

Hank

I had this same issue on my 930. You need to edit the bitmap with paint and make sure the dimensions are the exact same as the splash file. Rename the new splash screen with the same filename for the old startup screen and delete the old. That should fix it