It could be possible that the RAID card that you are using is taking some onboard resources, just for testing purposes I recommend to disable some onboard resources on your system such as the sound.
Make a firmware upgrade on the RAID card and also update the system BIOS , you can download the latest BIOS for your desktop board here:
Try to install the operating system without the RAID card on the desktop board, if you are able to do this, the problem might be related with compatibility problem between the desktop board and the RAID card
I have disabled the onboard devices and then I have managed to install XP on my raid 5 setup with no issues with USB ports.
Thanks a lot, your help was greatly appreciated.
You are welcome, I am glad to hear that I was able to help you