You should have a message along the lines of "5MSM Ver:A.3" near the top of the screen. If this is the case, a later BIOS can be found at
http://www.nix.ru/support/drivers.html?group=4&vendor=20 under SP-5msm (A.4) which supports disks up to 128 Gb.
BIOS ID string: 10/18/1999-SiS-530-2A5IMSMCC-00
BIOS OEM string: 5MSM Ver:A.4
INT13h Extensions...Present: new-style
=> BIOS already supports HDDs over 32GB!
Searching for SETUP size calculation routine...is already OK
BIOS already supports HDDs over 32GB & 64GB - Nothing to do!
Don't forget you may have to downgrade the UDMA mode to UDMA33 (Mode 2) using the HDD manufacturer's utility - see the post in Collected Wisdom on UDMA mode setting utilities.