If I remember correctly FAT32 supports drives up to 2TB (!!) in size. So Windows 98SE will support any size you can get right now.
However it should be noted that size of HDD is not so much limited by the OS than the BIOS. The BIOS is always the case which limits the size of the HDD installable. A quick update of the BIOS should fix these problems.
Smart guys are not smart; they only see things in different perspective.