missing shared dll.
unused file extension.
missing start up.
old start menu key.
installer reference issue.
invalid default icon.
missing start up software.
activ x com issue
All of these come up on registry scan.I have been told to delete as long as back up before hand.But i dont under stand what to fix(presumsbly this is then deleted)
Do i back up all of computer onto memory stick?,or back up all of these issues onto a CD somehow?

Hi, well firstly there is no detail in your post to reference what each listed entry is, CCleaner is a very safe registry cleaner, as safe as one can be when registry cleaning. Just make sure you always back up, and every thing should be fine.

You can also use erunt http://www.larshederer.homepage.t-online.de/erunt/ which backs up the registry on system startup.

When you clean the registry (an issues clean) you are asked if you would like to make a backup of the entries you are going to clean.

If you say yes, the backup is stored by default in 'my documents' and would have something like this as the title

cc _20091029_114628.reg

If there were problems after the clean just right click on that backup file and choose merge to put the entries back.

i use ccleaner for about 4 years, also i install it on every PC i get my hands on and it never caused any problem in registry, it's the safest & quickest !