First of all try plugging the laptop power supply directly into a wall socket and let it charge for a few hours to ensure the problem is not simply a faulty surge protector.
After a good charging period, try turning on the machine again and listen carefully for any sounds that the machine might make when you push the button. Take note of whether or not you hear the hard drive or cooling fans spin up at all.
Also listen for any BIOS beeps which can help indicate the source of any startup problems you machine may be having.
Another easy trick you can try is to remove the RAM memory from the machine and then reinsert the sticks right back into their holding slots in order to firmly reseat them. Often times a RAM stick will come loose and prevent the machine from booting up properly, and just needs to be reseated in order to correct the problem. Also try booting the machine with just one RAM stick installed if it has two in there normally. Try swapping out both in case one RAM stick or one RAM slot is bad. The RAM is normally accessed from a removable panel on the underside of the laptop.
You can also try unlocking and pulling out your hard drive assembly and then reinserting and reseating that as well for the same reasons.
It is certainly possible that your AC adapter power supply has failed, it is quite a common problem. You can always order a new one and see if that makes a difference. Here is a link to one available on EBay for about $17:
http://cgi.ebay.com/120W-AC-ADAPTER-POWER-SUPPLY-CHARGER-HP-PAVILION-ZD8000-/270510288004?pt=Laptop_Adapters_Chargers&hash=item3efbab6c84
Just use your mouse to click on the link, which is the underlined and highlighted text just above. This will open a new web browser page automatically for you and allow you to view the information and items at the website indicated.
Please comment back here to this page if you have any details to add, have any questions, have difficulty accessing the links, or just require further general assistance and I will respond as soon as I see it.
Thank you very much and good luck.
Joe.