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You could add it to the startup list in the registry, you would add,
"C:\program files\Ccleaner\ccleaner.exe" /AUTO
with the quotes, or you could also add it to the startup folder.
To add it to the startup, go into notepad and copy/paste this in there.
CODE
"C:\program files\Ccleaner\ccleaner.exe" /AUTO
Keep the quotes in there!
Save it as
anything.batTo run it for certain users, save it to C:\documents and settings\
"that user"\start>programs>startup
If you want it to run for all users, save it to C:\documents and settings\all users\start\programs\startup.
Hope this answers your question

(I've heard its not good to do this because sometimes files are stored in temp folders to install something and it may ask them to reboot but their files would be gone then, resulting in a problem.)