Generate key for a software

[chendur]

Hai guys, I ve developed a salary calculating software using vb.net.... Its working fine and i ve converted it to an exe file... My drawback is it can be copied and pasted in another system very easily... I want to generate a key for the exe file and while installing the key should be used and when installation is completed ,the key should not be used again... Is this ya secured one or give me some ideas how it can be done....