IDD CI24 ECONO MM Penta 1.20 Galaxy II 1.2Mtr Polar MTG yes it has been on the arc for 25 years and is now fixed on 13 East using two pairs of rusty molegrips. Unlike me they never groan but always perform.
I only know about PC's but if the bios (assuming it has one) or setup does not know that you have inserted a bigger HD then it will not know it has more space left. On a PC if the bios is not set to auto it will not detect the new HD and will think it is the old one. Maybe it is the same on this.... was your old HD 90GB by any chance?