Hi there, I'm Tim and will be assisting you today. I have over 15 Years as an Engineer and have been with eBay, DoD, and many others. I will do my VERY BEST to help you. If you like i can offer remote access and a call. In addition, with any positive rating I will support your question going forward for free.
Its because its not an HP powersupply, believe it or not, they want that extra $, thus it will not run with other PSU's.
here is a link proving thus, scroll down until you get to the beeps section
Damn, sorry to hear that. I'd have to venture a guess it may be the motherboard then.......I'd try and pull the cmos battery out of the motherboard for like 1 minute and replace, it looks like a watch battery. Do this with the HP powersupply in, maybe it will recognize it.
I can't connect......should be obvious. That's my canned hello response to everyone, so they know who i am, and what i can offer, it clearly does not count for everyone.... But it saves much time in letting folks know their options, yours is different.... thus we will need another approach. I can set up a call for 7.00 USD if you like to discuss this.