//remove limit and substring command below to process the entire string. depending on size. this could be a lengthy operation. no pun intended. 🙂

public static string stringtoconvert = "valuetoconvert";
public static int limit = 16; 

        public static string registryinfo_installer_products_key = HexToASCII(stringtoconvert.Substring(0, limit)).ToUpper();

        public static string HexToASCII(string ascii)
        {
            string hex = "";
            foreach (char c in ascii)
            {
                int t = c;
                hex += String.Format("{0:x2}", (uint)System.Convert.ToUInt32(t.ToString()));
            }
            return hex;
        }