New PC

Hi, I would like to re-register for the alpha sign-ups for Insurgency: sandstorm. I got a new pc with better specs.

This isn't really where you apply for the alpha. Maybe ask the community manager or message the devs/Sandstorm twitter account or something?

Why would you need to re-register? Couldn't you access your same e-mail address you used to sign up with? Find the e-mail with the key and re-download the game on Steam.