linux

First, I wouldn't suggest Windows 98, as it's no longer supported by Microsoft in any way.

However, to install a dual-boot system running any version of Windows and Linux, The first step is to either partition your hard drive in half, or get a seperate hard drive for Linux.

Second, Install Windows. You need to install Windows first, because the Linux boot-loader is intelligent enough to detect Windows and give you an option to boot it instead of Linux, if you so desired. The Windows boot-loader is only interested in Windows and will not offer you the same ability.

Third, Install Linux on the other partition or second hard drive. Linux should find your Windows Partition automatically. It might mistake it for DOS, but the end-result is still the same: you may choose to start Linux or Windows on the same machine.