Very weird-cant put mac pro to sleep

I tried to check all boxes except 'wake for ethernet access'...the display goes to sleep, but mac pro itself is constantly it seems, trying to shut down, followed by an irritating whining noise, which every few minutes. all the time it is in sleep mode..any help would be great...thanx

I have a question, not an answer...
How new is it? (thinking warranty here)

made in feb 2007...no warranty got a reply rumours that it could be the hard drive is failing...

any opinions out there?

As stated possible hard drive dying, also do you have a PCIE eSATA card or such fitted? These cards do cause sleep problems. Suggest running Apple Hardware Test over the machine.

ok will run hardware test next weeek when back from holiday thanks