First the master boot loader code is read (not an actual file on your hd, more like raw data at the beginning of the partition), which then processes the io.sys file. From there, I believe the order is: msdos.sys, config.sys, autoexec.bat, then win.com (actual start of windows itself and the end of the old DOS boot system). Now whatever gets run is kind of dependant on your system configuration. You should be able to get a log of what drivers are loaded by Windows using the bootlog option from io.sys (pressing F8 when it says "Starting Windows 98", then choosing "Create a startup log file"). If you are unable to reach the "Starting Windows 98" prompt, then most likely you have a corrupt io.sys, or the boot loader code is missing or that partition is not set as the active (bootable) partition.