You need to telnet into the switch, and issue the following commands at the prompts:
HP ProCurve Switch 5304xl# conf t
HP ProCurve Switch 5304xl(config)# int all
HP ProCurve Switch 5304xl(eth-x-x)# no lacp
HP ProCurve Switch 5304xl(eth-x-x)# wr mem
just type in the bits that follow the "#" sign, and make sure the prompts before it look the same (or similar).
Where it says (eth-x-x), the x's will be the beginning and end ports selected (which is dependant on how many ports you have installed).
BTW - this will disable LACP on ALL PORTS IN THE SWITCH.
Regards,
Shane.