yesterday my PC Pentium 4 desktop started beeping occasionally. It is just one beep about every 5 minutes. I haven't added any new software or hardware. Everything is working fine. I am using Zonealarm, Spyblaster, Adware, and Spybot and am not using a UPS. I am thinking it is the little battery on the motherboard, but can't find anything on the net that confirms this.