How to disable new version notifications?

go to Preferences -> Settings-User and add there: "update_check": false

EDIT :

If it's not working then add this line 127.0.0.1 www.sublimetext.com in your host file

File Location

Windows : c:/windows/system32/drivers/etc/hosts

Linux : /etc/hosts

Preferences / Settings - user

{
"update_check": false
}