Here's what I use to enable table fog on ATi Radeon cards under Win98SE:

Start > Run > type regedit > Ok
Navigate to HKEY_LOCAL_MACHINE\Software\ATI Technologies\Driver\000x\atidxhal
Right click on the empty space on the right side > New > String Value > type WFogEnable
Right click on the WFogEnable entry that you just created > Modify > type 0
Right click on the empty space on the right side > New > String Value > type ZFogEnable
Right click on the ZFogEnable entry that you just created > Modify > type 1
Right click on the empty space on the right side > New > String Value > type TableFogEnable
Right click on the TableFogEnable entry that you just created > Modify > type 1