geometry:drives are 1or more platters/disks, divided up into circular tracks,
divided into sectors,
there are different combinations of tracks disk sectors that add up to the
same size in MB if the bios recognises the drive with rifight size but the
wrong geometry it may write to occupied clusters, or non existent ones and
fail(or other 4 letter word starting with f) the disk, as long as the bios
recognises the disk correctly then those failures are very unlikely.

A hard disk drive is seen by the operating system as a string of
sequentially numbered clusters. However, the actual disk location is
referenced internally as a cylinder number, a head number and a sector
number. Drive geometry is the process where a cluster number is translated
into a cylinder/head/sector (CHS) reference.  Originally, this was a simple
translation dictated by the drive, but modern IDE drives can do the
translation in a number of different ways.  If the drive is configured as
AUTO then the translation _should_ be done in a predefined standard manner,
but this can't be guaranteed. Same applies to LARGE. In the worst case you
may have to manually enter the CHS values for the drive in order to make
them match from one machine to another.  The geometry settings are
established at the same place in BIOS setup that you saw that the second
drive was properly recognised.

For the new machine to assign a drive letter to the drive it only has to see
a valid DOS partition. So the fact that you aren't getting a drive letter
assigned indicates that it is not properly reading just the first few
sectors of the disk (which it should be able to do even if there were a
slight geometry mismatch).  Assuming the drive is working OK and is jumpered
correctly, then this indicates a major geometry mismatch.