Brought my Acer aspire one laptop back to PC world because the wireless was no longer working. They were very polite even though I didn't have the receipt, and went back a month in their costumer records to try and find the transaction. They did however warn me that it would have to go in for service which might take a week or so if it was over 28 days since the sale. In the event after checking with his manager, the person on the desk said he wanted to just try one thing.
To my embarrassment, after having Googled the problem and found that this machine can have wireless problems, he reached under the front lip of the machine and slid a micro-switch across which resolved the problem.
The moral of the story is read the manual before saying its broke.