"primary hard disc not found" "no bootable devices" message on cold start up , I have UPDATED the bios to (A16) and what ever DRIVERS i could find on the dell site, new main battery, when i get this message on cold boot I hit F2 and change the Boot POST:to min/auto/thorough and or change the PXE BIS Policy: to reset/accept and then save changes and it will boot up fine, now if i TURN it off for about 1/2 to 1 hour its OK but leave it off for a COUPLE of hours or over night this message comes back and back into the bios I go, also i noticed when i hit F12 for Dell Diag it said No diagnostic utility Partition found and I don't have the Dell "Drivers and Utilities" CD to boot off of -
any help     thanks in advanceYou need to remove the CMOS battery for 10 minutes...
Do this with ALL power unplugged.
Hit the power button 3 or 4 times as well to dissipate any stored energy.

This will re-set the CMOS back to it's default settings.Your particular laptop has a "RESERVE Battery".  It needs to be replaced.
http://support.dell.com/support/edocs/systems/latd600/en/ug/battery.htm#wp1045271