I agree with Kappy that your issue is with hard drive space, not RAM (memory), but if you should decide you need more RAM as well you can purchase it at a reasonable price from Other World Computing or Crucial.
For the issue of your startup disk being full the first thing to try is to empty your Trash. Lots of people put items in the Trash but fail to empty it, a necessary step for reclaiming that hard drive space.
If emptying the Trash still does not leave you with sufficient disk space, you can either get a new larger internal hard drive and move all of the contents of the current drive to it, or you can purchase a compatible external hard drive and move some of the contents of your internal drive to it.
Good candidates for things that can be moved would be your iPhoto library and your iTunes library, since both audio files and picture and video files tend to take up a lot of space. If you want instructions on how to do either of those, post back and we'll keep helping you.
Best of luck.
I do empty the trash permently. I had issues with my iphoto, and somehow ended up with multiple iphotos, which I'm scared to delete, due to pics that I don't/can't loose of my kids and work...I do however have an external harddrive but also, it shows that I have two Macintosh HD's??? I know....a mess? The closest apple store is 3 hours away, and being in school, single mom, and....yeah, I don't have much/any time to drive their much less pay to have someone clean this up? Any help would be much appreciated!
I work in the woods, so do lots of photography, so I'm sure that's the main issue of it being full.
Okay so follow this procedure to move your iPhoto librarie(s) to an external hard drive.
The iPhoto library can be located anywhere, but is usually found in the user's Pictures folder. Drag the folder called iPhoto Library to the external hard drive. This actually makes a copy. Do NOT delete the old one yet.
Launch iPhoto while holding down the option key on your keyboard. It will ask you which iPhoto library you want to use. Point it to the copy that is on the external hard drive. Test the use of this library fully, making sure all your pictures are there and it works as you expect.
Once you are satisfied with the newly moved library, you can move the old library (the one on your internal hard drive in - presumably - your Pictures folder) to the Trash and empty the Trash.
Repeat ths above procedure if you have more than one iPhoto library, moving each to the external hard drive, testing it and then deleting the old library.
A similar procedure can be used to move the iTunes library.
PS You should also consider backing up your pictures to more permanent media such as CDs or DVDs. This provides a backup in case of hard drive failure.
I had the same problem with my macbook that said the startup disk was nearly full. I followed the steps mentioned to move the iphoto library to an external hard drive and deleted the iphoto library on my HD. I then emptied the trash. I restart the laptop and all looked good, with extra memory and full access to my photos on the EHD. However, this morning, I started my laptop and got the same startup disk nearly full message. The size of available HD space shrank to a few MB. The iphoto library is no longer in Pictures folder and the trash is empty. What else can I do? What happend? Any help would be appreciated.