Hi Arun,
"CCleaner" is great as a junk cleaner and other things, but it is only a ok registry cleaner.
Wise makes a couple of free programs that one is a great registry cleaner, "Wise Registry Cleaner", and the other is like Vista's Disk Cleanup but better, "Wise Disk Cleaner". Here is the link for them:
http://wisecleaner.com/download.html
Shawn