I've had a decent record troubleshooting computers. This one is new to me. I don't know what direction to go to investigate.

Model: Toshiba Qosmio G25-av513
acpi BIOS ver 1.30

This is the messsage on boot:
RTC  Battery is low or CMOS checksum is inconsistent

I went into Cmos & set the date & time.
Chose 'restore defaults' before save & exit.

reboot gave me this message:
pxe-e61: media test failure, check cable
pxe-mof: exiting intel boot agent
Insert systems disk

Dropped in a legit copy of the Windows XP Media Center disk that the OWNER purchased.

Attempting to install a new copy gave me the message:
no HARDRIVES present. Installation must quit.
But Cmos shows the hd present.

I got a brand new compatible HD to replace the old one.
Noticed that there was no carrier bay for the old one.
Put the new one in anyway to troubleshoot (fit snugly)

Windows didn't DETECT the new one.

I tried locating the cmos battery to see if removing it momentarily would affect anything. Reason being that on any reboot the time & date reset.
 
I can't even find a website that shows it's location.

Here's the boot sequence I attempted:
hdd-fdd-cd-lan

Help?

I don't know what to try next.
Did you verify that the HDD is really bad? Sounds more like a BIOS issue. A bad HDD should not affect the CMOS date and time.
You really need to find a manual that shows where that little battery is located.

I was not able to find a repair manual on a Google search. Many sites came up that had everything but what you want.

But I did find this:
http://uk.computers.toshiba-europe.com/innovation/download_manuals.jsp


Please pardon the delay in response. Personal issues took precedence. But ala...no dice. Thanks for you help anyway. I'm chalking this one up as a LOSS.