Motherboard - ASUSTek A8n-VM, rev.1.xx
Bios - American Megatrends 0403
Windows XP Home, SP3
This has worked fine for several years, but now hangs at the ASUS screen on every start, instead of proceeding with the full boot. Pressing <DEL> there brings up the BIOS screen, which hangs at "auto-detecting device #01. Several hard restarts later, the BIOS will roll past #01 to #03, then automatically brings up BIOS Setup Utility. Pressing <ESC> there brings up a box asking if I wish to "Discard configuration changes and exit now?" Pressing OK there initiates the normal boot process, and normal computer function. I installed a new motherboard battery, with no benefit.
Any suggestions?, please.

perhaps your hdd has died. Try putting a bootable CD like a linux live cd or the windows installation CD/DVD in and see if it boots. If your hard drive is the problem then it's not too hard too put a new one in and your data is most likely lost.

I don't see how the hdd would be faulty, since the computer functions quite normally once I get past the startup problem. Thanks for your interest.

are you saying that the PC sometimes boots from the HDD?