Bluetooth radio was usually an 'extra-cost' option and if it is not shown on your support site, it was not included. Bluetooth is seperate from WLAN, although Fn/F2 turns both on/off (or how it's set in BIOS).
Another check would be to go into BIOS Setup (Fn/F3 in Windows, or F2 on first Dell Boot Screen) and page through to see if it is there and set to 'load' on startup ("enabled" might be the word to set).
You need to look at your Dell online Service Manual to see installation, you could look for the 'card' or the 'cable' to exist.
It can be a problem with 'license' to add Bluetooth after purchase, which is why internal BT is not found through Dell Upgrade site, some have ordered from Dell 'Spare-Parts' or bought on Ebay.
thanx for the reply
i checked my bios and bluetooth card is not present in my laptop but in wirelees tree there was a setting that enable or off the internal bluetooth, it was off by default, i changed it to enable and also set the <fn><f2> key to wireless + BT option,
what is internal bluetooth, and after i have changed this setting still my bluetooth is not activated and no light is seen with the wifi one.
Click Here to open the Bluetooth page<ADMIN NOTE: Broken link has been removed from this post by Dell> from your service manual.
the above shows what it looks like and where it would be found in an Inspiron 6400.
If it existed and were enabled, you could turn it on w/ Fn/F2.