Hi Hitman4HireTN, do you have the 6-3 digits of the new and old cards with you (these can be found in the white bar code sticker on the adapter)? maybe you can post it here so we can help you check out for some clues on why it's not working on the specified system. Also, have you tried to compare the BIOS settings of the computers w/ issue vs those w/out issue? have you tried disabling on-board adapter on the Dell systems.
hope this help.