updating iTunes and it says there is not enough space on the startup disk...what can I do?

Freeing Up Space on The Hard Drive

1. See Lion/Mountain Lion/Mavericks' Storage Display.

2. You can remove data from your Home folder except for the /Home/Library/ folder.

3. Visit The XLab FAQs and read the FAQ on freeing up space on your hard drive.

4. Also see Freeing space on your Mac OS X startup disk.

5. See Where did my Disk Space go?.

6. See The Storage Display.

You must Empty the Trash in order to recover the space they occupied on the hard drive.

You should consider replacing the drive with a larger one. Check out OWC for drives, tutorials, and toolkits.

Try using OmniDiskSweeper 1.8 or GrandPerspective to search your drive for large files and where they are located.

Since you started with "I don't know what a startup disk is or how to delete files from it to gain space", it will be nearly for us to help you online. I suggest that your ask your local Apple Store for assistance.

A startup disk is the disk drive from which you boot up your computer when you use the Power button. If you don't have other hard drives externally connected to your computer, then it is usually the internal drive - the one inside the iMac case.

Nothing wrong with that idea. 😀