Thanks for your time LR,
I am happy to give it a go, can't stand the thought of paying a fortune for an engineer to relpace something simple.
I have removed the graphics card, wireless card and network card and still get the same noise.
I have been searching the web and trying to follow a Dell diagnostic procedure (not easy), which is indicating a USB issue? The machine was dismantled for decorating and I can't be sure the USBs were replaced in the same ports (there are only the mouse, keyboard and a dongle). It seems the cure is to remove all USB devices and reset the BIOS. I also found reference to a possible problem with the actual memory, but not convinced on that one. I am currently trying to establish how to reset the BIOS and what it means?
Thanks for the link.
Cheers,
BB