how to start a windows application before windows login(not as service)

hi all,

i got a application that reads data from serial port and insert it into database and just make a log entry(system date) into text file. The application is running fine when i set up it on windows start up.when the windows starts the user has to enter windows log in and then the application starts.

But now i need to start this application before windows log in so that the user need not enter user name and password each time the windows starts to start the application.Also i can't remove the windows user name and password.

I have tried using it as a windows service but eventhough the application started it was not reading data from the serial port.Also i have tried it adding the exe as a key into regisrty run. but it too didn't worked.

Can anyone help me on this..