M/B P5RD1, CPU Celeron 2 Ghz, 764mb, 2 HDDs & CDRW. CDRW set as Sec. Slave. Assembled abt 3 yrs back. Now, when I try to boot it up, the HDD LED continously remains on and CDRW light goes on and off every 2 secs. Nothing else happens, no sound from speaker or anything. Checked Battery, Memory Cards, HDDs and CDRW and all are working fine. Any idea? Thanks in advance.
You don't mention this, so it is unlikely, but it COULD produce your symptoms. IF you have a floppy drive, and IF it is set as one of your early boot devices, and IF you accidentally reversed the way its data cable plugs into the back, you'd get this result. The boot sequence would go to the floppy drive but get nothing but communication errors, so it would keep trying and lock itself into a loop, without ever finding a place to boot from.
Just as another thing to try, check the jumpers on all your IDE devices. In fact, just in case one of them is making poor contact, remove and re-insert each of them (several times each) one at a time. A clash of device identities on an IDE channel can cause errors that produce a failure to boot.
I also like amnotanoobie's suggestion of dead PSU.
By the way, the former performance that it beeped once as it completed its POST is the normal signal that there were no problems encountered with hardware during the POST. The fact you get no beep at all right now says it has not found a hardware problem during POST so far, but it still cannot complete the boot sequence. In fact, it may not even be finishing the POST process since it fails to give you that "all-OK" single beep.
Replaced MoBo with Intel D915GAV and things are working fine. I checked the Manual dor P5RD1 and it says it has Crashfree BIOS, meaning if the BIOS gets corrupted, you can over-write the BIOS file with a fresh copy, using either floppy drive or cd drive. I downloaded latest BIOS file and copied it to a CD and tried to over-write the original BIOS file. However, the CDROM just continued to blink every 4 secs. or so and nothing happened. So, I decided to replace MoBo. Thanks everybody for suggestions.