I am not possitive on this, but I think I may have read somewhere that a processor with HT shows up as two CPU's when you open taskmanager with certain apps. Under the processes tab Right-Click a running process, click Set Affinity... to see the number of CPU's are running.
I have a Dual-Core, otherwise I would check it out myself, and as long as one can determin which programs do not support DC processors, the non-supportive apps. can be individually set to run on only one CPU. An example of this is Open Office, at least the version before this last release anyway. It was very buggy under the DC, but after changing the affinity to 1 CPU, other than hogging my RAM, it worked great.
Just some food for thought,