Desarrollar software para windows desktop / develope sw for windows desktop

It's simple project ! I need make a APP like windows form with compability for windows xp, 7, 8, etc... The idea is the next (All validation are webservice connection - the service exist not necesary create) - Login Screen( user and pass ) check WS Show banner for news (the news obtain from WS) - In the menu have 4 option for users - Make sale (Put number of client and confirm , select carrier) make the sale with WS process, i want to send ticket to print and show screen with the result - Check last 30 sales (Result obtain from WS) - Make pay of service (put company, carrier , reference number) WS, i want to send ticket to print and show screen with the result - Make register of deposit ( the user select bank, ammount, date, autorization, number of store) insert into ws The 4 options are easy , but the system need obfuscate code , and for example if the user install in computer X and press register machine , the system save in WS the MAC ADDRESS and don't be able to use in other machines, only this. This is a difficult of the system. I need creativity and easy to use for the users. 5 DAYS TO FINISH AFTER ADJUDICATE. NO MORE, I'LL APRECIATE IF THE DAYS ARE LESS.