windows proxy credentials prompt windows 7

I am a student at a university and I have to access the inteet through their proxy servers. I set the settings in "inteet options". I am using an etheet cable (though wifi had previously worked). I have inteet access but:

• In web browsers I get prompted for my password twice. In the first time I need to enter domain_name/user_name and the second time domain_nameuser_name.

• Some programs like Skype require me to enter credentials and only domain_name/user_name works

In the "windows credential manager" in the control panel for some reason it doesn't save my full password but only 8 characters (I am not sure if it only saves 8 characters or only shows them) and is set with domain_nameuser_name.

I am aware that domain_nameuser_name is the correct way and don't know where it accidentally saved domain_name/user_name as the useame to use. This is all very weird for me because I can't figure out why in the world domain_name/user_name should ever work. I am also having problems with different programs accessing the inteet (for updates and such), I do not know if this is because the proxy blocks certain ports or because I can only give the program 1 user name and password to use, and so it can't authenticate twice like I do manually with web browsers and then gets stuck not being able to access the proxy at all.

I have been googling and looking for answers for a while now and am going nuts. If anyone has any clue where I might have some settings wrong or what I can possibly do I would be very greatful.

p.s. Don't know if this matters but the proxy is set with HTTP, SECURE and FTP under port 80