How to Adjust TxPower

Hi all,
We deployed wireless network running Win2003, Cisco
AP1200 aironet , Wireless client - XP and PC Card - Orinoco Gold a/b/g The
problem we face is that we have a good signal strengh but we are not
authenticated , we are authenticated when we have excellent signal strengh
only.We have noticed that Orinoco Tx power initially start at 100dB and then
goes down to 30 dB. /it is set up to 100dB at the utility
Then , we are trying to set up the Tx Power debugging the driver but still
no success.

Does anybody knows to set up Tx Power on the machine running Windows XP

Thanks for any help
Mariela Donkova