glVendor problem

I admit I’m stumped and feeling stupid. Want to verify getting hardware acceleration from ny Voodoo. Here is my code (abbreviated)

const GLubyte *vendor_name;
vendor_name=glGetString(GL_VENDOR);
sprintf(cOutBuffer, “fps %0.1f %s”, fps, vendor_name);
What I get in my window bar is: (null)
Tried everything (usually get page faults)
Admit my C++ skills are rudimentary.
Please post your working code.
Thanks (I am so humbled by this you would not believe)