One slave HD is showin 2 drive letters?!

Here’s the deal:
OLD Config:
windows 98se
IBM deskstar 15 g as Primary1 – Master with slave setting
IBM DeskStar 30 g as Primary 2 – Slave setting
CDRW as Secondary 1
Secondary 2 – NA

NEW Config:
windows 98se
IBM deskstar 15 g as Primary1 – Master with slave setting
WD 60 g as Primary 2 – Slave setting
CDRW as Secondary 1
Secondary 2 – NA

Every thing was fine in a previous config.
In new config the WD 60 gig shows up in Explorer as both drive letter D: AND
F:!
WTF?
Device mangier only shows the 2 type 47 drives!
Bios shows only 2 Harddisks.

I have the latest bios and drivers for the MB (Biostar M7VKD).

How can I get Explore to recognize the primary slave as only one drive?
Does WD HAVE to be the boot drive? I hope not.
Thanks in advance,
PW