RAC won't find Vista PC's

Am i doing something wrong, or not?

After installing our first Vista Business and putting on domain, in RAC it won't find the PC. Ensured PC is logged on as an administrator and all sorts.
The only way i got to install is by creating the package to file then installing that file from the PC.

Not a worry for me in this situation, but what about when someone has a network of 500 new vista machines, they can't go around to each machine to install NOD one at a time.

Can anyone provide a solution for this or else prove me wrong??

Thanks