Assuming that you have tested memory on the Tested Memory list below:
It can be the memory slots on the board are faulty.
Last test to try is to reduce the system to minimum out of the chassis if possible.
Try to see if you still get three beeps without the memory.
Then try to do a CMOS clear and BIOS recovery.
If everything fails, then may be the board memory controller is faulty.
Since this is an old server board, i have never used it before.
Anyway, i got the information how to do a BIOS recovery.
Please follow all the instructions on the PDF file below. Page 58/108
Download page for Bios: http://downloadcenter.intel.com/confirm.aspx?httpDown=http://downloadmirror.intel.com/13056/eng/SE7230NH1_BIOS_NH1340P.zip&agr=&ProductID=2162&DwnldId=13056&strOSs=&OSFullName=&lang=eng