if you want to use the latest software, microsoft's .NET 2.0 has had serial port support added back into it, in the System.IO.Ports namespace. so if you use the (currently free) VB.NET express edition (which is based on the upcoming .NET 2.0) you can use it... or you can wait for the new Visual Studio.NET 2005 to be released.
It's a lot more elegant interface than it was in many previous versions of VB, which usually was sort of "hacking" to get it to work. I interfaced a serial port to VB6 a couple years ago, but it was pretty confusing, and the program I ended up with didn't make much sense, although it worked.