Dell Dim 8400 can’t get through POST

This machine worked until stored for a few months. Have checked battery voltage (=3) and reset the CMOS jumper and checked bios settings including reset to default. The BIOS version is –03

Usually–not always–the machine stops at this point:
[some issue]
“Strike the F1 key to continue, F2 to run the setup utility”
No response to keyboard beyond this point.

Sometimes, boot attempts go no further than a blinking cursor at the top left.

Other info:
The time/date tends to revert to 2004.

Sometimes the event log contains:

CMOS Battery Failure
CMOS Checksum Error
CMOS Time Not Set
(but this does not happen on each boot cycle.

Any suggestions?

Thanks…