Probably the hdd needs a bit more time to spin up or warm up. BIOS is ready to go, but the hdd is not.
There are a few BIOS settings to try, to slow down the boot up process.
One is to put the floppy drive and CDROM before the hdd in boot sequence. Another is to disable Quick Boot (it can be called something else in your BIOS, such as Quick POST). Another is some BIOS settings give you the choice of boot delay - set the number of seconds for the delay, but your BIOS may not have that option.