I am not here to complain about NIIT. But in my experience please do join a MCA program instead of a GNIIT.
Number one reason. This is most important. MCA program affliated to an indian university is recognized all over the world. NIIT programs are not. It can be a supplement ONLY.
Usually NIIT trainers are not experienced, even if they are experienced, they may not have real experience working in a software company. Thats true for MCA program too. If the trainers can actually work in a company they probably be making more money than they are training. But the key point is MCA program is recognized all over the world. You can buy a computer for the amount you pay NIIT. do MCA and pretty much use eclipse IDE, c++, java which are free to download and learn.
Try to learn C++ as much as possible, this is the key language. Rest you can pick it up on your own. All the language follow object oriented principles and has basic items that are pretty common in programming languages. So its easy for you to do programs in VB.NET C#.NET and Java once you have C++ experience. Trying to join a course just for C# is a rip off.
Another key area to learn in Databases. Try learning MySQL and Oracle (if possible). All the other databases in the world will follow almost same principles.
Hope this is useful.