Continuous Beeping (not listed in beep code tables)

Dell Inspiron 5100 laptop, running Windows XP. A couple of seconds following power-up, a rapid and continuous beeping begins. There are no breaks in the beeps, the rate is about 4 every second, and they continue for upwards of 60 or 70 beeps. The screen is black apart from a white horizontal bar near the bottom. The bar contains equally spaced vertical strips, and during the beeping, the black strips gradually disappear from left to right. Eventually, Windows start-up begins as normal. The laptop and all functions appear to continue as normal following start-up. I have not installed any new hardware or software prior to this problem occurring. My concern is that each start-up may be harmful in some way or worsening the problem. My questions are: 1. What has caused this problem? 2. How can the problem be remedied? 3. Is there any chance of harm being caused to my laptop from this error? Thanks, Steve.