My software update isn't working...It shows that there is an update necessary and then when it starts downloading, it says that the iTunes package connot be saved and then it stops the update..What do I do?!
If you have plenty of free space on it (say at least 20 GB or 15% of its capacity) then you can try running Disk Utility's "verify disk" test. If it finds any problems, follow the instructions to start up from another volume & repair them.
In the Utilities folder, the Disk Utility application has the "verify disk" test. If it does show an error, you will need to boot off of your original Snow Leopard Install Disk and run Disk Utility from there.