SYSTEM.INI
WIN.INI
SYSTEM.DAT
USER.DAT
AUTOEXEC.BAT
CONFIG.SYS
MSDOS.SYS
PROTOCOL.INI
IO.SYS
EXPLORER.EXE
COMMAND.COM
You can also download and run Microsoft's Emergency Recovery Utility for Window 95 & 98 which will backup these files automatically.
REMEMBER, YOU ARE TRYING THIS AT
YOUR OWN RISK!