When does the beeping start? When the RAID controller loads? As soon as the system is powered on? As you discovered, there is no SYSTEM beep code like you describe - it is the RAID controller. Is this plugged into a UPS? Try booting to CTRL-M, Configure, View/Add ... IF asked to choose between Disk View and NVRAM, choose Disk, then save on exit. Go to Objects, Adapter, Disable Alarm
I'm new here, so if this is in the wrong forum, please let me know (or move it to the right place). I recently bought a used PowerEdge 2800 rack mounted server with dual 3.6G Xeons, 12GB of RAM, embedded raid controller, two 146G 15K SCSI drives (which are probably empty), and both DVD and Floppy drives. There is no operating system, it's been out of actual service for some time, but seems to power up properly. I can enter the bios and RAID screens. I have ZERO experience with servers; this is the beginning of my journey to learn. The problem I'm facing is that very shortly after powering on, it emits a loud beep. I researched POST messages, but the beep I'm getting isn't among them. The system give one long beep (maybe two seconds long), followed by an equal time of silence, followed by another equal length beep. I realize that I need to correct whatever is causing the error, but it's kinda hard to work on the system with it screaming in my ears. Can anyone tell me what the system is trying to tell me, what subsystem is generating the beep, and, most importantly, how to turn off the noise? Thank you in advance, Tenaya 
Poweredge 2800 Continuous Beep at Power Up