Hi,
1. Which domains are you trying to connect to?
2. Can you access the same websites using Internet Explorer?
3. Exactly what are you typing in the open blank screen (is it in command
prompt)?
The 400 Bad Request error is an HTTP status code that means that the request you sent to the website server (i.e. a request to load a web page) was somehow malformed therefore the
server was unable to understand or process the request.
Also refer to the link.
Telnet:frequently asked
questions
http://windows.microsoft.com/en-US/windows7/Telnet-frequently-asked-questions
Provide us the required information so that we can assist you better.
Hope this helps.