Visual Studio 2005 is the new version of Visual Studio 6 that is completely redesigned to work with the .NET technology. Visual Basic 6.0 was a part of Visual Studio 6 family which is a quiet different platform. Starting fro Visual Studio 7 (2002), Visual Studio has switched to .NET platform and all the languages included in it, ie. Visual Basic.NET, Visual C#.NET, Visual C++.NET and Visual J#.NET are now .NET based languages. Visual Basic too has got incredibly large amount of changes and it will not be wrong to call it a completely new language, although some similarities with the previous version remains for easy switching of platform for developers. No Visual Basic is squally powerful as any other language on .NET platform.
Visual Studio 2002 was targeted for .NET 1.0 platform, 2003 was at .NET 1.1, and like wise 2005 is targeted at .NET 2.0 platform. Similarly, VS 2008 is targeted at .NET 3.5 platform.
Now What happened to .NET 3.0 then? Well, After the much redesigning that Microsoft has done to the platform from version 1.1 to version 2.0, the platform (which is an independent thing from Visual Studio, mind it) has now come into a state where there will be no extravagant changes in the architecture in future. .NET 2.0 and 3.5 don't remove or change anything in .NET 2.0, they just add features to its feature set (this was not the case with 1.1 and 2.0, 2.0 changed a lot of things from 1.1). Hence Visual Studio 2005 can be configured to Work with .NET 3.0 too, but not with 3.5 i think.
Along with that, the new Visual Studio 2008 has the ability to compile your project for .NET 2.0, 3.0 or 3.5. You can choose it in your project's properties. So with this release, Microsoft has made sure that if you buy VS 2008, you don't need to have 2005, you can have all its features + the new ones.
Now, starting from the 2005 version, Visual Studio is also available in Express Editions which are scaled down, but quiet powerful versions or the Full Visual Studio and can be downloaded and used for free for non-commercial, learning use. in express edition, you do not get all the professional tools and you do not get an integrated IDE for all languages, instead you get one ide for each language you work upon.
And ya, don't be confused, Visual Studio is a family of products while Visual Basic is a part of it. Visual Basic 6 was in Visual Studio 6 and Visual Basic .NET 2005 is in Visual Studio 2005. Visual Basic 6 was not that powerful and was plagued with many different shortcomings and problems. Visual Basic.NET 2005 is a very powerful language with all the features of an Object oriented language.
And ya, full installation of Visual Studio 2005 with MSDN takes around 4.3 GB of hdd space, so as a safe value, keep at least 5 GB free on the drive.
I hope i cleared your confusions.
