What do you do with customers who don't have or can't find product keys for Windows, Office, etc.? I find the majority of people who ask me for help fall into this category. Unless they have a laptop with the product key stuck underneath, they rarely can find their original product keys. I'm then faced with telling them they need to shell out hundreds of dollars or switch to Linux. Some of the them switched, but unless they're willing to learn Linux, that's a whole new set of problems (e.g. they call you saying "I downloaded MSN but I can't install for some reason").
For Windows, you tell them they need to order recovery CD/DVDs from the manufacturer, and then we order them for them. It's usally between $15-25. If we happen to have restore disks from their manufacturer that will work with their model, we use them, so long as the computer had a valid copy of windows on it to begin with.
If it's a computer they've built rather than bought from a big box and have lost their key, well, they're out of luck, but most people who build their own computers don't bring them to a computer repair shop.
