u should use a registry defragmenter.... it will make ur system work little fast.... they relable products like System Mechanic did some very good job here....
I guess System Mechanic is very good. Moreover defragmenting your registry is a good thing. But first and foremost backup your registry before defragmenting it.
defragmneting the registry is definately a good idea. and u too must do it. its absoluely safe.
here are some utilities which have registry defragmentors in them or are stand-alone ones :
registry compactor
registry compressor
tune-up utilities
system mechanic
all avlbl at www.download.com