I've just got Abexo Free Registry Cleaner and it looks safe..it is very effective.. Think I got it from PC User DVD

There are millions of registry "cleaning" programs. Both Freeware and Shareware. Some good, some just dangerous.

If there was any data left behind in the registry (after uninstalling a program) that is likely to cause a problem - most "registry cleaners" will normally delete or fix the offending registry entries.

One of the easier to use (and safer) cleaners is CCleaner http://www.ccleaner.com (which has a number of other useful features too).

Alternatively if you know exactly what you are looking for using the windows program regedit.exe or regedt32.exe will allow you to edit or delete individual entries in the registry (definitely not recommended for beginners or the risk averse).

Despite the fascination people have with cleaning the registry - in most cases having a few extra entries should not cause you too much grief. Many people actually believe that cleaning the registry will result in little or no quantifiable benefit at all.

Playing with cleaners etc without backing up first may result in your Windows setup being unbootable and requiring a reinstall. (To Backup Registry - see ERUNT )

Some relevant reading (2 alternate articles on the merits of cleaning your registry)

1. Cliffs Notes On Freeware - Are Registry Cleaners Safe to use?
2. Ed Bott's - Why I don't use Registry Cleaners

I found comments following the Ed Bott article to be interesting reading.

I like new softwares. After remove that softwares, there's something in registry. How can I delete it?