G'day,
You might have a hardware/driver incompatibility problem.

Hold down the F8 key as Jon suggested & then choose Step-by step confirmation from the menu. Choose No for some of the options until you find a combination which works OK. Keep trying until you narrow it down to one device.

Some suggestions:-

Choose Yes for Process the system registry.

Choose No for all entries in autoexec.bat & config.sys. (ideally a win9x system should not have either although most do. Get rid of them if you can)

Yes for Create startup log file. It might tell you something.

Yes for Load the Windows graphical user interface.

Yes for Load all windows drivers, but then No for each of the individual drivers (usually *.vxd files).

Keep doing all the above but choosing Yes for more drivers each time until you narrow it down to one device. Then you still have a problem, but at least you know what's causing it. What you do next depends on what you find.

Cheers,
Alan