The HT will be (number) x the bus speed. Actual HT would be 2x that. So, if you have the 'Hammer' multi (I think it's called in some BIOS) set to 4x and you have your bus at 300 your HT will be 1200 (2400). As for it being correct, check the specs on your CPU. I know some of the AM2's have 2400HT, but it's probably not going to be lower than 2000. Only AM2 chips I seen with less than 2000HT were the BE's, (low-low watters).
Another thing you might consider, OP, is have you tried a different Hard Disk? Maybe run HD Tach on that one. You may have a failing drive or some problem with the interaction of the HDD and the mobo.