I have downloade the trial version of RegVac (latest release) it seems to work well on 64-bit Vista Ultimate Edition, however when I go to the clean Software section and it starts scanning for obsolete software entries it just freezes there-it keeps on going and going...Is this software really tested and compatible with 64-bit OS ? Please let me know as I like the application but cannot really use it

Yes, it is tested and compatible with 64-bit OS.

Quoted from Ray Yes, it is tested and compatible with 64-bit OS.

Thank you very much for the prompt answer, I was just wondering why does it hung in the Software cleaning section ? Works OK with the other sections, especially with the registry ones, any ideas ?

   That is Vista.  Vista, "for your protection" blocks or slows down certain areas in the registry.  RegVac does what it can to use other methods to access the data but sometimes Vista just does not allow it.
   I would suggest that you try waiting longer.  If Vista reports that RegVac has stopped responding, ignore the warning and allow RegVac to continue.  RegVac does not respond because it is busy working.