EMac seems slow - Do I need/can add more memory?

Question

I have an eMac 1GHz PowerPC G4. It's already about 4 years old, so I have collected alot of music, pictures and files. It seems that now it takes a little longer to respond. I constantly get the rainbow swirl thing waiting for files to open. It definitely slows down if I'm running Photoshop or Illustrator AND iTunes at the same time. iTunes seems to be the reason it slows down in general (especially if its iTunes and another application)
I have 768 MB of RAM already (the 256, and a 512). Can I add another 512MB of RAM? Is it necessary and will it help? If I look up the memory usage, it always looks like I have very little available (currently I'm using 87% of my memory and while applications are open, I'm only using FireFox)
Also, I have 47.43GB on the HD available.. Should I invest in an external hard drive?
I'm not sure if this is a memory problem or if I need more HD space..
Thanks
Kirsten

Answer 1

Tiger will run quite nicely on a 700 MHz eMac with 640 MB RAM, which suggests a software conflict with an automaticly launching system or user utility. Non-Apple add-ons that put anything in the menubar (e.g., haxies) in particular as likely suspects. If you Start Up in Safe Mode, does the Mac's performance improve noticablly?
As roam noted, using Activity Monitor (as an admin user, show all processes, and sort top-down by %CPU usage) can help identify if some process is eating up clock cycles. For instance, if you have Classic running in the background with an extensive Extensions Manager set open, you may see TrueBlueEnviron in the Activity Monitor running at 80% of CPU usage (in which case, use Extensions Manager in Classic to turn on only the absolute minimum of extensions you need, rebuild the Classic desktop, and close Classic when not in use).
Check your third-party software add-ons (items that appear under the "Other" heading in System Preferences when using View by Categories). Check the publisher and/or Version Tracker or MacUpdate for Tiger-compatible updates. Try disabling startup items temporarily (move to a holding folder and restart) and see if that improves performance.
Try creating a troubleshooting-only admin user account with no add-ons and see if that runs faster; if so, that points to something inside your normal user account's Home folder. Use Preferential Treatment to check if your normal user preferences are damaged.
If the new account is also slow, look at the System and Library folders at the root level of the hard drive, checking e.g. /Library/StartupItems and /Library/PreferencePanes.