adjusting headset height

[rain]

I have a Giant OCR 1 which has a threaded headset. (I'm not sure why it has a threaded headset, it's a 2005 road bike and according to my web search manufacturers switched to unthreaded in the late 90s.....)
I am trying to raise the headset but can't find instructions on how to do this. Any ideas?

I'm in the process of trying to find a new position that will help with the soreness I get in my neck and lower back. I'm really enjoying being able to make my own adjustments to the bike, it makes the bike less daunting not to mention it's incredibly fun. but please let me know if you think this is something that should be done at a bike shop. Thanks.