|HDD did not fit. Had to modify Network Adapter. I disassembled everything. removed the lock that prevents the IDE and Molex connector to be removed. Used wire cutter to cut the lock and filed the rest. Removed extra tin that restrains movement of screws.
At first boot, HDloader wanted me to format the drive but it gave error "Could not format drive". nevertheless, rebooted PS2 and using HDLoader, it was able to detect the drive without any games. Tried loading Orig Battlefield2 on the drive. Success. Tried Playing it.. no quirks. everything going fine so far. I guess I'm just lucky