The best way to prevent that particular problem is to list the item as a fixed price rather than as an auction and to require immediate payment. Then the buyer must pay at the same time they purchase the item. You may have to use the advanced listing form to ask for immediate payment.
I see that on your current listings you offer worldwide shipping which is something that I would never offer for a $1200 laptop...I would have shipping for the US and Canada only. Anything over $850ish must be sent with a signature required in order to be liable for item not received protection and that is very expensive and may not be available in some countries.
To be honest, I'm not sure that I would sell any type of electronics worth that much money of ebay as that one category does seem to have more fraud than most other categories.