I can't log into my minecraft account! Please help!

I deleted minecraft off of my computer including the .minecraft folder, and when I open the launcher, the play button is grey and will not let me play, and for the profile it says, "(Default)." Also on the bottom right hand side where it says,"Welcome, Guest! Please log in. Ready to download & play Minecraft 1.7.9" it will not let me log in please help me I am so frustrated because i cant play until this is all figured out!