There are a lot of applications out there today that were built using Visual Basic 6, Microsoft’s last version of Visual Basic before we released the .NET framework. In fact, there are several companies that still use VB6 as a development platform for their solutions. While there are many good reasons why people are developing solutions in VB6, the VB6 platform no longer has wide reaching support from Microsoft and this can cause an issue from a maintenance perspective (VB6 support reached end-of-life state in April of 2008).
For that reason, many people that have been developing VB6 applications are migrating to VB.NET. This process is not necessarily an easy one (I speak from personal experience having worked with a team to migrate a very large VB6 COM+ web solution to VB.NET in the past). While the syntax looks very similar, there are a number of things that can cause problems for VB6 developers moving to .NET, including the leap to fully object-oriented software design and development.
If you are a VB6 developer looking for information on making the move to VB.NET, my colleague John Hinz on the Canadian ISV blog has a great post on some of the resources that can help you and I encourage you to read it. Specifically, he highlights a launch page on MSDN with links to guidance for upgrading VB6 applications to VB.NET, a code advisor for porting VB6 apps to .NET as well as highlighting some of the incompatibility issues you may run into when porting your VB6 solution to .NET.