|System idle is supposed to register all the CPU cycles that aren't being used by other processes. |
I didn't suggest you run the registry module in Ccleaner. The default is the cleaner module.
If you think that a registry cleaner that removes more entries is superior then you don't know much about the process. You want to remove orphan files and that is it. Aggressive cleaners can disable your Windows installation for no good reason.
Again, 384MB of available RAM is not enough.
Boot into Windows safe mode and see how the computer runs there?
Are you running SP3? If so, I suggest you use Windows Security Essentials instead of AVG. AVG is a good program but it is taxing your system which doesn't have enough RAM as it is. WSE is light on the resources and is free.
I suggest you run msconfig and disable some of the items that are running. You don't need programs that search for updates to your programs, for instance.
AVG may be set to scan while you are trying to do other things. Try WSE.
What is the percentage of free space on your Windows partition?