there is most certainly always a diffrence either in the placement of the screw holes or the internal chipset, bios, list of acceptable cpu's or any number of things. best thing to do is pay the 15% restocking fee from ebay, and then go buy the motherboarrd from HP or a certified reseller of NEW parts, the ebay parts such as motherboards are almost 100% reflowed or in some way refurbished without doing the propper work to them to make sure that they are 100% new, if you look any place on any of the chipsets and see a burning or a scorch return it asap without even checking if it works or not, its been used and sold at 2/3 of new cost. Likely that HP will give you a great discount if you want to send the laptop to them and have the technicians do the work, and get it back in about a week...be sure to check their work though with prpper heat sink setting and compound use.
the origional laptop motherboad for my dv9500 was 450.00 before tax and shipping, the cost for me to send to hp and have them repair...300.00 same board same repair. IF the cost is higher than usual, tell them yu need a HR satisfaction manager to talk to, generally they will lower the cost by 100.00 to make the customer happy.
hope it helps, and to those of yo uwho use ebay as a major supplier of aftermarket major components good luck also, ive had such bad luck with component knock off brands, and just out right used merchandise that i will not use ebay for major component repair source anymore.
questions feel free to ask, also hp has a nice site that you can use to find the right motherboard for your laptop/desktop by simply putting in the S/N or the P/N , that way you know exactly what you need before you mistakingly order the wrong part.
ocy