Start-Up Tone

I'm getting about a 7 second constant tone upon start-up and no bios screens, monitor stays blank.

The system is old, was bought back in at the end of '03, will be used mainly for emails, chatting, etc., basic stuff. It's an off the shelf system bought from Staples, with of course an unkown motherboard (the only thing that's really listed on it is S651M rev 2.3), a 350W power supply, 1 gig of pc2700 ram (2 x 512mb sticks) (added sometime after)..but not sure if the mb can even handle the ram, might only be able to handle pc2100 stuff, but don't have any of that laying around anymore. The bios sticker says it's a Phoenix BIOS D686 version.

I've disconnected the hard drives, reseated the ram, video card, all fans are running as well. All connections have been checked as well and are in tight, still same tone.

I've tried looking around several sites, including here for the answer to the tone, but no luck, anybody have an idea to what the tone is telling me???

Ok so changed the battery, and that worked for a bit however the optical drive wouldn't start-up the Win Xp pro install disk, swaped out a back up drive to see if another one was working, then it went right back to the 7 second tone..did a voltage check on the old and new battery..both show power..weird.

Gonna rip apart the system and check voltages with the ps and others..if all that is fine, not sure what else to check..anybody??