Fail to install curb gem in windows7

Fail to install curb gem in windows7

curb gem fails to install.
C:\RorProjects>gem install curb
Building native extensions. This could take a while... ERROR: Error
installing curb: ERROR: Failed to build gem native extension.
C:\Users\abc>gem install curb
Temporarily enhancing PATH to include DevKit...
Building native extensions. This could take a while.....
ERROR: Error installing curb:
ERROR: Failed to build gem native extension.