With the larger chains I have had no trouble with returns, they infact normally give a 10 day cooling off period but this does also mean that you should not damage the packaging too much.
Just last week I upgraded my router for one that cost ¥15000 from PC depot. When I got it home I found that I could not flash DD-WRT to it.
I took it back within two days and got a no questions asked cash refund.
On the other hand I bought a device for ¥9800 in Akihabara on the main drag. These guys know that most people can't come back so tend to sell them returns or duff products.
The owner was being an ass and refusing to accept the return. I knew the owner could speak English so I told him I would stand outside his shop telling tourists he sold bad stuff. At that moment a Korean guy and his wife were in the shop, looking to buy the same model I was returning.
I started to tell the guy not to buy it as it was defective and he should go someplace else to buy it.
The owner pretty much shoved my refund into my hand and told me never to come back
I agreed with him and will never return to that con artist shop.
BTW, I had bought from there before and had the good sense to try it out before getting my train. I waited in the shop while they had to open over 5 boxes to find one that worked!!!
I should have learned the first time.