Try shutting the computer down normally, and then remove the power cable for a few minutes. Then power up as normal. Please mention the version of Microsoft Windows.
Lead removal for a minute or so has worked for me for various problems in the past.
If it doesn't this time then maybe you need to check the control panel / system / device manager, look for red crosses or yellow exclamation marks, especially around USB items.
Seems methyl wins the best answer prize as indeed a complete power down AND remove the cable was the solution. First time I have heard of that but will remember in the future.
Old_Geezer : the offending USB was there but was impossible to remove/update or do anything.
zbearspirit : As I said the system hung and I had just run system restore before this pesky message started.
Many thanks to one and all and I now bang away on my keyboard in veritable silence :)
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