Support and demand for Wifi on a Linux enterprise server system (RHEL based) is generally limited and usually a desktop system requirement, for which other more suitable Linux distributions exist.
You need to be 100 % about the model of your Wifi adapter.
What is the output of lspci -v related to your Wifi adpater?
Does the driver you download support the Oracle UEK2 kernel (2.6.39)?
You could try your installation starting the system from the original RHEL kernel at the Grub menu to see if it makes any difference. If HP support nor the OS installation provides a driver for your hardware, check http://elrepo.org/tiki/tiki-index.php which focuses on hardware related packages to enhance Enterprise Linux.