Cleaning the registry is thought by many to be of little benefit. Deleting the wrong entries can cause problems.
However, I do it. If you want to do it, I advise being careful of the big commercial programs, unless you are able to check each entry before deleting.
Ccleaner is a good app. - I do not advise it's registry clean option on 7.
I use Glaryutilities - free version available here: Glary Utilities
I have been using the registry cleaner in Glary on 7 x64 without any problems - it is quite gentle and I have never had any problems with it.
Glaryutilities also automatically makes a backup. It includes a lot of great modules, such as a file undelete tool , disk space explorer, and a registry Defrag module.
I use the Glary registry Defrag. module on Vista, but not on 7.
This is because the Vista partition is the System partition as well as the Vista Boot partition.
However, the 7 Boot partition is obviously different from the System partition. I do not recommend doing a registry defrag across drives/partitions.
You may like to check in Disk Management to see which is the System partition. Confusingly, this contains the Boot files, bootmgr. and BCD - this is the partition thru. which all your installed Windows operating systems will be booted.
The Boot partition is the partition containing the operating system files.
Hope it helps