Kika, the method of mconway actually does not need any name/pass!

as conclusion based on pmurgs and mconway here is the method. They explain quite laconically, so there's no way to get what they say if you did not do such thing before... blablabla....

In Win7 I did like that:

1. In tray, right click the Network icon, option "Network and Sharing Center", or fin the same in Control Panel if you are not lazy

2. On the left side of the window at the top, should be three options, select the middle option "Change adapter settings".

3. Here should be also your PPoE connection (having in gray something like "Huawei Mobile Connect - 3G Modem"). Roght click it and select properties.

4. In the Properties window, Options tab, you must uncheck "Prompt for name and password...". and also the rest, in Dialin Options.
(I also checked "Include Windows logon domain", not sure if it is needed but it works on mine with it checked.)
Redialing options(you can change if you like): 5 attempts, between redials: 5 seconds, idle: 1h

5. Create somewhere a file like "internet-on-logon.bat"
and put the line:
Script:
START Rasdial <connection name> <username> <password
in my case it was:
Script:
START Rasdial "Internet Everywhere_ADM" 
The name I took from the window from step 3, rightclick the connections, "Rename", and copy the name, without renaming anything;
I put the name with quotes, because of a whitespace in the name;
I put no user / pass because I had none on my 3G connection

6. Create a shortcut to the .bat file and move it to the Startup folder

Now there should be a connection on logon!
Good luck!