'txtsetup.sif is missing' may mean the CD reader could be missing it.. I've found that a file missing message displayed during an installation, usually means the CD Reader may be missing it, or the CD may have burning errors. If the Installation CD is original, the reader is probably missing it, if it's a bootable slipstreamed copy, it may be a CD burning error.
To guide you in enabling the IDE Native I would need to know the specific motherboard brand and model to locate the mobo manual which may include BIOS instructions. The BIOS ID code could also help to search for a BIOS manual. For now I can only tell you the setting should be under the Chipset BIOS menu, down to OnChip SATA. This is for AMIBIOS but it should be named about the same on other BIOS brands.
To get the BIOS ID code, start the computer and during the BIOS post, freeze the screen with the Pause/Break key when you see a long alphanumeric code, and copy that code,.. then search for the manual and post the code here to give you a hand with the search.