Deauthorizing?

Will deauthorizing my own iTunes account in the process of deauthorizing other computers delete any of my songs or have any effect on my library?

No.

(51170)

Do I have to do it from my old PC?

If you have five computers authorized, you need to do it from there or via the Deauthorize All command. If there isn't an Apple TV involved, you're done after authorizing the Mac; nothing needs to be reauthorized.

(51171)