I am using Delphi 7 but I have trialed the Delphi 2005 - 2010 versions.
In all these new versions my CPU utilization is 50% (one core is 100%, the other is \"relaxed\")
I guess first step would be to try to identify which part of delphi is taking 100%. Is it the main thread, or a secondary thread? If you manage to identify which thread is hogging all the CPU power, I guess you could debug the IDE (Attach to process from a 2nd instance of delphi, can be D7 so you won't have 2 apps flooding your CPU), and then step into the "offending" thread. With some luck, the code executing could have some debug information indicating what is being done.
If you have any 3rd party/Home components installed, try removing them.
Like already mentionned, try disabling code insight.
Try disabling any anti-virus running. (Maybe some kind of Live-lock)
That's all I can think of right now...