It's good to clean temp folders, browser history and so on. Just don't use the registry cleaner or you'll mess up your programs and operating system.
You should avoid Registry Cleaners, Boosters, Optimizers, TuneUp Utilities... There is no need to clean the registry and this type of software will do a lot more harm than good. These utilities do not only remove what they think are orphan entries in the registry but legitimate items still in use will be deleted in the process, causing irreparable damage to some programs and the operating system.
Keep in mind that they will always find "errors" to fix, even on a fresh Windows install!