Have learned a lot trying to buy computers and parts on ebay. 

1) Computer dealers RARELY ever sell a good or fixable computer on ebay - if there was nothing wrong with it they would just sell it locally.  If they claim it "has not been tested" - you should laugh, not bid - I learned the hard way several times.  Their ads might look good, but I keep getting cheated by these computer businesses.  I have bought several computers from the businesses that have multiple bad parts that could not have all gone bad at the same time.  They just loaded up a laptop with a bunch of their defective parts and sold in on ebay claiming it "had not been tested."  This is just plain lying and out and out fraud where I come from. 

2) Computers that post to bios can still have motherboard problems!!!  I have bought several laptops that had motherboard charging problems even though they still posted to bios. 

An easy way to sell a computer screen with a scratch or bad pixel is to list it on ebay, pretty hard to tell in the auction photos and the seller can always claim "it wasn't that way when I shipped it."

3)  Return for refund guarantees often have you spending a lot of shipping money and the seller is out nothing.  He just relists it until someone does not send it back.  I bought four mother boards from a place in Pennsylvania.  They claimed they were in good working condition and had been tested, but all four were defective.  Reading their older feedback, this seller sold these same boards months ago - they were returned and they just re-listed them on ebay.  Imagine the trouble we went to - replacing, testing, removing and returning the mother boards - even had to file a pay pal claim STILL trying to get the money back.  The seller knew these were bad when they shipped them!!!  Ebay does nothing about these crooks.

4) Often times, sellers will not send you the item pictured or it will be in a lot worse condition than described.  Do not bid on a "perfect" item and expect to receive a perfect item - you will be sorry.  I recently bid on a "PERFECT" laptop keyboard from a computer business in Indiana - they not only did not send the one pictured in the auction, but send a broken piece of junk - missing keys etc.  They claimed they grabbed one out of the "wrong pile".  Then they expected me to send it back (paying $9+ in shipping to return a broken keyboard they sell for .99 cents).  Pay pal still will require me to send it back to get a refund.  I will have to spend almost $10 to get back a total of $19.99???  Even though it was their "mistake" - I am the one who is going to lose money, not the computer dealer.  Computer dealers often use this old BAIT and SWITCH scam - beware. 

5) PAY MUCH MORE ATTENTION TO NEGATIVE feedbacks.  If the seller has 100 positive and 8 neg - he probably cheated eight people and others were just afraid to leave neg feedback.  Or they were not smart enough to see through these seller explanations.  "sent the wrong item, send it back for a refund", "sent the wrong item, return for a replacement" (see #3).  "It worked when I had it" etc.  I even had one dealer tell me that even though he misrepresented the computer, that was too bad because it was still a good deal.   I got ripped off again.   

6) Even though they describe it as being in wonderful condition, sellers often hide a little "no warranty, no return" clause in their auction.  If a seller has confidence in their item, they will insure it and refund your money if the item gets damaged in shipping.  No insurance often means you are probably getting something the seller "knows" is bad. 

7) Sellers are usually the worse packers imaginable.  I have received at least 25% of my parcels with damage either on the outside or the items inside.  Sticking a computer in a slim priority mail shipping box and expecting it to not get thrown, dropped or tossed during shipping is just plain stupid.  The post office will not pay a recent insurance claim saying an item has to have at least 2 inches of packing around the item - yet they accepted it from the seller & INSURED it in a post office priority mail box that is only 3 1/2" inches thick (how can you put 2 inches of packing around an item - 2 + 2 = 4 and put it in a box only 3 1/2 inches thick)???  SURE the post office will let you BUY insurance, but they will not pay the claim!!!

8) Remember the most important rule.  WHY WOULD ANYONE TAKE APART A GOOD RUNNING COMPUTER???  Seriously, unless the part is worth a lot more than a complete computer - BEWARE.  If a computer is missing the screen and they are trying to sell you the bottom - BEWARE.  Again, why would someone take apart a good running computer???  Go ahead email and let me know, I keep falling for this and I keep getting cheated.