My first real eBay failure

I have to admit that things did not really go according to plan with my recent eBay purchases. I have been attempting to build a new PC from eBay spares, but the Motherboard I bought decided it was not going to work after initially booting up successfully.
This was a disappointment, and to be honest I am not sure if it was the mobo, or my CPU that failed, but there are no signs of life and I have had to go back to the drawing board. Not to be put off, I am already bidding on another mobo/CPU bundle (!) and am determined to emerge with a working system. I have promised myself that once the new system is up and running, I will have to clear out any remaining computer debris from my loft. Currently this comprises four Motherboards, three CPU's and various power supplies.
I have described this as my first eBay failure because usually eBay sellers are very good at refunding when you have out of the box failures - my problem was that I knew full well that when it arrived, the mobo did actually power up and it is only since I tried fitting it into a new case that it decided to fail. So I cannot in all honesty threaten negative feedback when the seller has sold a working board in good faith.
To expand on my recent experiences with eBay, I also recently had someone sell an item I had bid on (and won) to an off-eBay customer, which to say the least was disappointing. This was the first time ever that I have left negative feedback for anybody, and I have just reached the 100 transaction mark...