Sounds like you have a broken pin or loose jack housing solder joints in your DC power jack. This is a very common problem with laptops of all makes and models of laptops.
the majority of laptop DC power jacks are soldered directly to the motherboard, and are not easy for first timers to replace.
Any repairs that you attempt to do yourself are at your own risk, but ive tried to lay this out as easy as possible so you can see what you are in store for.
You are in luck with this if you want to repair this yourself. it can be done, but if you have never disassembled a laptop before i would recommend highly that you familiarize yourself with the
HP Dv9000 service manual
and with this guided tutorial
of disassembly. Just so that you will see what is involved.http://cegeekbook.blogspot.com/2010/01/dv9000-disassembly-tear-down-part-1.html
-----Proper antistatic measures are strongly advised. Touching the motherboard anywhere but the corners could cause a static discharge, destroying your motherboard.Its also highly advisable to wear a grounding strap while working on this.
Things will come apart, but sometimes it takes patience.
If you still feel up to this after looking over the tutorial, and looking through disassembly section of the service manual, then ive rounded up a short list of parts
if you want the entire assembly, this is the best route to go, unless you enjoy soldering and saving a few $$
This is a drop in replacement for your defective power assembly.
Used $12.99+ $4.73 shippinghttp://cgi.ebay.com/HP-DV9000-DC-Power-Jack-Cable-432985-001/220505822432
New around $50-$70 depending on source
On another note, a qualified repair shop that services laptops can do the repair for you for between $100-$150. This includes the replacement DC power jack, but not the power assembly that ive listed. A shop will just use your existing power board and wiring. Ive done replacements on a good number of these and they are not as bad to do as the majority of other notebooks.
Hope this helps, and if i've helped you, please dont forget to take the time to rate.