Buying Computer Components
A lot of computer owners purchase speakers, routers, case fans, modems, cables, etc. Very often some expertise is required in order to know whether the device or component they are buying is going to be compatible with their computer.
Anyway, I know a person who once bought a heatsink for his PC, but he was not really convinced it will be compatible. When he tried to install it at home, he noticed that he was right, and that indeed it was not compatible. He returned the item to the computer store.
What you can learn from this story is to buy computer components only from stores that allow you to return items. That is because there are so many different brands and products that you may never know if that specific component will be compatible with your computer.