Slow iMac: too much ball spinning!!!

Question

I have a two-year old 20" Intel Duo Core 2.0 GHz iMac with 1GB of RAM. My problem is that for the last 6 months, the iMac has become progressively slower and slower operationally. I have no complaints about browsing or download speed, but simply moving from one application to another.
For example, while playing iTunes, it took 8 seconds from the time I pressed the volume control on the keyboard until it actually registered on the screen and the speakers. In Mail, when switching from one user to another, it took 17 seconds of listening to the hard drive grinding until the mailbox was changed. It took 45 seconds to connect my iPod and later it took 25 seconds to disconnect it.
Not to belabor the point, but while I was writing this, I loaded iPhoto (80 seconds), then loaded Finder (25 seconds) then within Finder switched from Home to Desktop (50 seconds). Lots of disk grinding and ball spinning.
Maybe I need more RAM, but nothing has really changed since I bought this iMac. I haven't added many new programs or added a gazillion photos. I remember thinking how fast it was when I first got it. I haven't even used half of the hard drive. I regularly restart the iMac hoping that will clear things out and help. But it doesn't.
I appreciate any words of advice. Thank you.
JA

Answer 1

Upgrading the RAM would be the cheapest and easy upgrade you can do. About $25 to add a 1GB dimm. http://eshop.macsales.com/item/Other%20World%20Computing/5300DDR2S1GB/ How full is your hard drive?
1. Repair Disk Permissions- Open Applications/Utilities/Disk Utility select your hard drive on the left then under the First Aid tab click Repair Disk Permissions. This is something that you should do periodically especially after installing Apple updates.
2. Verify Disk- Again open Applications/Utilities/Disk Utility select your hard drive on the left then under the First Aid tab click Verify Disk. If it fails Verification yo will need to boot up to your Mac OS X install disk in order to run Repair Disk.
3. Maintenance Tasks- Make sure that your maintenance tasks have been run: http://docs.info.apple.com/article.html?artnum=107388
If you shut down your computer every night it's likely that they have not been run in a long time. I like to use Onyx: http://www.titanium.free.fr/pgs2/english/download.html
Start with this let us know how it goes and we'll go from there.
George