If they see the value in bitcoins and believe it will rise, it's not crazy if they are accepting bitcoins.
If the computer is worth $500 for example and they are selling it for 5BTC, they see that they can easily exchange it to cash if they want too without making a loss after fees. Or, if they chose to keep the 5BTC with them and wait for it to rise, they will make even more money by taking BTC as a payment.

From the wiki, you will see that:
New bitcoins are generated by the network through the process of "mining". In a process that is similar to a continuous raffle draw, mining nodes on the network are awarded bitcoins each time they find the solution to a certain mathematical problem (and thereby create a new block). Creating a block is a proof of work with a difficulty that varies with the overall strength of the network.

You may read more about it here: https://en.bitcoin.it/wiki/FAQ#How_are_new_bitcoins_created.3F
There is also a Mining category (https://bitcointalk.org/index.php?board=14.0) here so that you can see how people actually "mine" bitcoins.

For those who are novice in backing up and writing scripts to copy your credential away from your personal computer, you can try using dropbox. It lets you sync with the online network and you can also do a local network sync to your other computers. However, you need to be extremely careful with your dropbox password or which computers you chose to sync your dropbox with.

OP, hope that you will find your passphrase someday. Keep trying.