I have looked in the download folder and found multiple copies of the latest update of iLife.
Then you need to delete all but one of them and install it.
I have also tried to uncheck the automatic software updater and change it to manual update or to change it to weekly, but it does not accept the change. Maybe I need to reinstall it? Will osx lion take care of this problem?
So it appears your preferences are corrupt for Software Update. You can delete them and then set it up again:
1. Quit Software Update if it's running.
2. Go to Home/Library/Preferences and delte the com.apple softwareupdate.plist file.
3. Restart Software Update and set it's preferences the way you want, then quit.
4. Restart Software Updatte and check to be sure your preferences stayed the same.
As for reinstalling, that would not solve the problem. Likewise, installing Lion wouldn't do it either, and there's no compelling reason to install Lion, unless and until you're familiar with how it will change existing applications and your overall user experience. Spend some extended quality time at the Apple Store exploring that before you even think of installing Lion.