http://www.geocities.com/enigmadeadsouls/softfsb.html - the old SoftFSB - maybe the motherboard is old enough to be supported.
You are not going to turn a 600 celery into a super-beast
You might get nothing at all (no supported adjustable PLL).
You may well hit instability very soon as the PCI frequency rises with FSB - this can also result in IDE data corruption, as the IDE interface will also be overclocked.
And you could trigger a catastrophic failure.