PowerEdge 750 memory upgrade - Registered or Non-registered?

Looking to upgrade the memory in my PE 750 to the 4GB max.

I get that it takes 1GB PC3200 ECC 128x72 CL3 unbuffered DDR 400 184-pin RAM.

What I would like to know is:

1) Can it take PC3200R? (not sure what the "R" is. registered?)

2) Can it take Registered, or only Non-registered RAM?

Thanks,