Dimension 4100 bios

Hi all. Sorry this system is kind of old, but got this little problem hopefully someone can help. I have two old Dimension 4100. One is running XP with 512mb max. Upgraded bios A03 to A11 2 years ago. Trying to rebuild my 2nd Dimension to donate to local kindergarden, also upgraded the bios to A11. Problems now, both computer can't boot from CD rom. I believe after the bios upgraded. I tried with numerous CD-roms. Boot to Win98 boot disk, can see CD rom, copy WIN98 folder to local C: drive. Run setup from local C: inside win98 folder, says setup needed to run in Microsoft Windows. I have downgraded both computer's bios from A11 to A03, still couldn't boot from CD rom. Here are my questions;

1)is there any bios flasher that can erase the serial key in the bios? (I don't have extra sound card, so I swap the motherboard that have sound card build in and kept the mb that have PCI sound card)

2)Is there any boot disk that can turn the boot disk to Windows base? Is there any super boot disk availabe to download?

3)Is there any 3rd party bios that can make my CD-rom bootable or anyone know which version on dell.com for dimension works?

Thanks!