I used this card:
SYBA SY-PEX40039 Controller Card - Newegg.com
(On sale till 2/9/15 for $9.57 & free ship With Promo Code EMCANAP65)
It is a bootable card. Not sure what kind of sata card you tried to use.
You can get an exact replacement HP board (Pegatron M2N78-LA (Violet6-GL8E) from eBay or amazon, but it'll cost over $100. and it still might have the same problem later on as the board your replacing.
You might be able to get away with replacing the board with another board with the same chipset....sometimes it'll work and then again, maybe not and you'll need to re-install windows.
The front panel header shouldn't be much of a problem, there are little tabs on the block that the front leds and power button connect to. You can open this tiny tab with a dental pick and the wire will come out easily. You can then add/remove wires to the proper location on that block. Do not bend the tab more than you have to because it can and will break off.
Just take the front cover off the case and see what wire color combinations go to each led and which ones go to the power switch, you can figure what goes where from there