Dell Proprietary Special 19-Pin to Standard USB / HD-Audio / HDD LED Front Panel Cable for Dell Inspiron 5675, OptiPlex 3040 3050 790 Q87 7010 7020 9020 (30cm)
This cable allows you to convert the special Dell proprietary 19-Pin front panel cable to standard HD-Audio / HDD LED connector for regular ATX motherboard.
If you want to use a Dell case with regular ATX motherboard, then this is the cable you need.
DELL-S19-USBAU