1.) What are the differences between VB.NET and VB?
VB.NET is a modern, object-oriented language. VB (Classic) is its predecessor, and it's no longer actively maintained.
I don't know if that is what you are looking for, but a technical comparison can be found in Wikipedia:
2.) I need to develop basic apps for Windows.(like a notepad) Which one should I use?
VB.NET. However, if you already know Java, the C# syntax might be more familiar to you. From a functional point of view, VB.NET and C# are almost equivalent.
3.) Is there an IDE available for both?
VB.NET applications can be developed with Visual Studio, the most recent version is 2013.
The VB Classic IDE is unsupported as of April 8, 2008.
4.) If possible can you suggest me a good resource for learning VB or VB.NET
This is off-topic for Stack Overflow.