Hi I have a similar problem but cannot find the code or lights on the dell troubleshooting manuel.
The tower starts gets to a green b yellow c yellow d green and then beeps like crazy, the beeping is continous so i cant find a continous beeping code, and wondered what might be wrong.

also when i look at the abcd lights, it starts beeping on the above, but then changes to others and slower than normal will reach all green??

cheers for all help
chris