This BIOS is specifically for HandBook 486 SX25 machines that are having problems with the external floppy drive. If you are not experiencing a problem, you will not need this file. Boot the system clean (press the F5 key during the boot process). In the directory that you copied the BIOS update to (or directly from the floppy drive), type in its filename (bios125.exe). This will automatically update your HandBook 486 BIOS. Version 1.25 (9/99) may include unspecified updates, enhancements, or bug fixes.