memory

Applications folder>utilities>activity monitor> click on system memory. You'll see memory usedavailable memory on a pie chart. OR do a Spotlight Search, in the search field type in "Activity Monitor"

To free up space would be to create more space on your hard drive - it has nothing to do with memory. You can add more RAM (memory) if your computer allows it; but that does not create space anywhere.

So, is your hard drive getting filled up? If so, you need to leave a minimum of 10 - 15 GB of empty space at all times for the system to work properly - more space is better. Please post back with your total hard drive space and how much is left (empty).

Simply click Activity Monitor to read System Memory and determine how much RAM is being used

Your "HD" is your hard drive and that contains "Storage" for data, Not "memory", which is the amount of RAM you have. Your hard drive is essentially full beyond the point of your iMac being able to run properly. You need to offload a lot of files (photos, music, movies, maybe?) to an external hard drive to free up space.

OS X needs about 10 gigs of hard drive space for normal OS operations - things like virtual memory, temporary files and so on.

Without this space your Mac will slow down as the OS hunts for space on the disk, files will be fragmented, also slowing things down, apps will crash and the risk of data corruption - that is damage to your files, photos, music - increases exponentially.

Your first priority is to make more space on that HD.

Nothing else can be done until you do. Purchase an external HD and move your Photos and Music to it. Both iPhoto and iTunes can run perfectly well with the Library on an external disk.

iTunes:

http://support.apple.com/kb/HT1449

iPhoto:

http://support.apple.com/kb/PH2506

After you've moved them and made sure that it all works, you can delete the original off your hard drive. Remember to empty the trash - if you have a lot, do a few at a time. If you still need more room, check for other space hogging files and delete or move them.

joanne987,

A couple of words of caution, first you need to have a backup plan to protect all of your valuable information (photos, music, movies, financial records etc....) If you use Time Machine (TM)that is a great start, however when it comes to backup redundancy is extremely wise. Many folks on these forums use TM and also create a bootable clone using either Carbon Copy Cloner or SuperDuper. Backups should be kept on physically separate HD's. The reason being is hard drive will (not might but WILL) fail. You don't want all of your backup on one physical external HD.

Next is NEVER and I mean NEVERkeep data on the same external HD as your backup. The reason being is when the EHD fails you will not only have lost your valuable data but it's backup.

This means you should have no less than 3 EHD's right now. One for your data (photos, movies, music, etc..) the second as a TM backup drive and drive number three is for your bootable clone. While cost may be a consideration, when you lose all of your precious data, the last thing on your mind will be the money spent on EHD's, it will be on the relief that you didn't lose your valuable data.

He is saying "if your data and backup are on the same disc, when it fails you lose both"

You have described your computer as having a 160GB internal hard drive which is currently out of space. It appears you have an external drive already with a time machine backup and movies. How big is the external drive and is there anything else about your setup you can share? Did you check the folder size of your pictures and music? You've asked this problem on a couple of different threads now.