Dell L400 and boot priority

I've a strange problem.
When I try to boot, the notebook try starts from LAN!

If I enter the BIOS, in the BOOT option I seen all the lines grey and it
doesn't allow me to modify it.

The warning on the right-side of the monitor says me:

"All items on this menu cannot bee modified in user mode. If any items
require changes, please consult your system Supervisor."

There is any password at user or supervisor mode.
I've tried also to reset the BIOS detaching the backup battery.
No way...

I'm allowed only to press F12 and a boot menu is accessible and provides all
four options:

1. Removable Devices
2. Internal Hard Drive
3. ATAPI CD-ROM Drive
4. Network Boot

If I chioce (2) the laptop starts fine but I can't store the setting.
WHY?

Thanks.

 

I've solved re-flashing the BIOS...


Anyone knows where to buy a cheapest BIOS backup battery?
Thanks

 

Never been inside an L400. What type of battery is it? Fedco in the U.S.
sells all kinds of batteries at pretty high prices. Try eBay? ... Ben Myers

 

It's a standard button battery. I buy all mine at the Home Depot for
under $2. Try your largest local home improvement store.

 

Not exactly.
It's a cluster of button batteries maded from Varta, 7,2V 15mAh

The battery production was ended.

Now I'm able to found them only on Ebay at over 30-40$...

BIOS upgrade was most chepest...