Win 98 only starts in safe mode

When actually in safe mode, the words safe mode shows in the four corners of the screen.

More likely that Windows has replaced your Video driver with the default VGA driver which gives the same screen resolution that you get when in Safe Mode.

Actually do boot up in safe mode [by hitting F during the boot process and select safe mode. When there go into device mamnager and check what video driver it shows. Remove it, if more than one remove them ALL [this is mandatory] and then reboot.

Before you do this be certain that you have the correct video drivers or know the path to point to it.

take it you mean in "device manager" does not show any conflicts??? - never-the-less from memory if you are in safe mode you wont get any conflicts shown anyway - to add/confirm what Ray has said - it sounds like a driver problem - most probably your graphics card - but i would make sure u down load ALL the lastest drivers for your machine and systematically do as Ray has suggested.
Peter