Tablet Help With Tablet OS

I was given a cheap nasty tablet from family member after it was dropped it wouldn't turn on so opened it up checked all connection inside and found lose batt connector so pushed that in and it works again

But now it seam stuck on the boot screen with white ANDROID_ on the Screen

When i was inside tablet i noticed on mainboard a 4Gb SD card that's fixed this must be were the android OS is installed what i want to do is find a version of android that i can replace the original with as i think it maybe buggered and not loading

When i remove it and boot device it wont load boot screen with white ANDROID_ then when its in it seam to stick on this screen

Anyone have an idea of a suitable version i can use and safest way to extract it to SD card so that it works

Hope some can help us with this