Being able to find something the instant you need it is important!
I have an Outlook contact for each app installed on my laptop. When I received the post-purchase confirmation email, I copy/pasted the codes and other information into the notes area. When I need a code (like recently after installing a new hard drive on my laptop), a quick search in Outlook, copy, paste. Done.
No need to find a document and look for the code. Finding something in Outlook is so much quicker, especially since it’s always open.
This is especially important now since we rarely get the actual software DVDs. Back then, I’d write the code directly on the disk with a sharpie (and still created the Outlook contact).
How do you keep up with your codes? Let us know in a comment.