People go into computer stores and say things which aren't even remotely true. Replacing a component on the strength of what a customer said would be thoroughly foolhardy, if the hard drive isn't faulty then something else is, and replacing the drive wont help anyone.
A new drive is under £50 sure, and reinstalling windows doesn't take many man-hours. Carefully backing up their data, scanning it to reduce the chances of preserving viruses, putting it all back in the right places and setting it up so it looks much like it used to does take time. Changing the hard drive over can take anywhere from 30 seconds to 20 minutes depending on the laptop, and it's not unreasonable to want to take the drive out to run diagnostics on it.
£20 minimum charge sounds very cheap to me. You're going to look a right fool if the drive itself turns out to be fine, or if there are other significant problems with the laptop, and you've told him you can definitely fix it with no problems for the price of a new drive.
A new drive is under £50 sure, and reinstalling windows doesn't take many man-hours. Carefully backing up their data, scanning it to reduce the chances of preserving viruses, putting it all back in the right places and setting it up so it looks much like it used to does take time. Changing the hard drive over can take anywhere from 30 seconds to 20 minutes depending on the laptop, and it's not unreasonable to want to take the drive out to run diagnostics on it.
£20 minimum charge sounds very cheap to me. You're going to look a right fool if the drive itself turns out to be fine, or if there are other significant problems with the laptop, and you've told him you can definitely fix it with no problems for the price of a new drive.