Fastest? For your Celeron or your P4 or your 32 bit processor? Or for your Xeon's or 64 bits?
It really doesn't make that much difference for most people as the processor you use will have more of an effect on your program's usefulness than whether your wrote in VB or C++.
If, however, you are looking for the faster software to code, then VBnet is still the choice of many (self included). And with the current release of VS 2005, the languages all compile to the same or near same executable code. (Windows programmer, can't speak for other languages)