How do I add a python script to the startup registry?

import webbrowser
webbrowser.open('www.youtube.com')

Get rid of all of that _winreg stuff. Instead, you (assuming double-clicking on a py file opens the console) should simply place it in your startup folder (C:\Users\yourusername\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup on Windows 7, and C:\Documents and Settings\yourusername\Start Menu\Programs\Startup in XP). This works because Windows tries to open all files in the startup folder, and if Python opens PYs by default, Windows will open the Python console. Try restarting, that should work.

Baboon: I am a little late posting, but you seem to have left off the sam at the end of your code here.

When you open a key you need to add the user rights, if you do not _winreg defaults to "READ":

Here is a snippet from the python site http://docs.python.org/2/library/_winreg.html#access-rights

sam is an integer that specifies an access mask that describes the desired security access for the key. Default is KEY_READ. See Access Rights for other allowed values.

Here is the code corrected:

 import _winreg, webbrowser
    key = _winreg.OpenKey(_winreg.HKEY_CURRENT_USER,'Software\Microsoft\Windows\CurrentVersion\Run',_winreg.KEY_SET_VALUE)
    _winreg.SetValueEx(key,'pytest',0,_winreg.REG_BINARY,'C:\Users\"USERNAME"\Desktop\test.py') 
    key.Close()
webbrowser.open('www.youtube.com')