Did this problem start suddenly or just build up over time?
More RAM would certainly help but that machine was fairly sprightly to begin with and should not take forever to switch between programs.
A lot of converts (switchers) from the Windows world have developed the habit of clicking the Red X, at the top right of the application window, to make the program quit.
Although there is a Red button, top left of the application window, in OS X; it does NOT quite the application. The windows are closed but the program is still running. Those little black triangles under the icons on the dock indicate what programs are running.
Having a lot of programs running will soon chew up 512MB of RAM and leave your system frantically moving data on and off the HD to make room.
Take a look and see if this could be the problem.
If it is not, it may be time to consider an Archive and Install of the OS. Note a big deal and all your data will be preserved.
My wife's macbook is running really slow and since I'm used to working with windows I don't know how to help her. She has a 2ghz Intel Core Duo processor with 512 mb ram. She's running Mac OS X 10.4.1 and has about 10 gb of free space on her HD.
I know she could probably use more ram but its so slow I'm not convinced this is entirely the problem. After reading some other threads I repaired permissions using the disc utility but that didn't seem to help much. Basically the computer takes forever to switch between programs, save open documents etc. Iphoto just kept quitting on her as well.
I am hoping someone out there may have some advice?