C# Keygen and Source

My program is currently protected by checking 3 different text files on my 110mb.com account. It checks for the username using XOR encryption, it then checks the password. The code for getting the machine code(HWID) in my program is as shown here

MachineCodeString = "MOD" + "-" + IPreplace3.Remove(3) + "-" + replace4.Remove(4) + "-" + IPreplace3.Substring(IPreplace3.Length - 4, 4);
            machineCode.Text = MachineCodeString;

the ipreplace stuff and replace is just removing 0's, :'s and .'s

I was wondering if any of you could program a keygen that only requires a name and serial. Depending on what the user enters for the name, the serial would have to match using an algorithm.

I would like the Solution(source) in a PM so that way I could learn how this was done and implement it into my program. Thank you and I know for some of you this is extremely easy adn could probably get done in about 10-15 mins. I'd appreciate if this also could be not very easy to crack because I plan on selling my program. Thank you in advance