VXI cards are, by specification, plug and play, so I'm not exactly sure what you mean by a "non plug&play card." I'm guessing that the card is effectively a VME card. In this case, you can just add the VME device in the proper configuration utility. Here is a link to a document on our website about configuring VME cards (http://ni.com/support/vxi/vmeinfo.pdf).
You should easily be able set the slot, pseudo Logical Address and memory space. Once configured, you should be able to write to registers using NI-VISA commands (viIn, viOut, and viMove). These high level commands are included in the highreg.c example which shipped with your NI-VISA software (installed in vxipnp directory).
I hope this helps.
Trey Hamilton
National Instruments
Applications Enginee
ring
http://www.ni.com/support