I encountered an error on a few machines when I was installing Visual Studio
SP1.

If you have gone into Add/Remove Programs and removed Visual C++ from your
installation. When you attempt to install the Core SP1,  SP1 tells you that
you have no components installed.

I got around this by reinstalling the last install. (Select Reinstall from
the Studio Setup)

There's got to be an easier way. But this worked for me.

-james