Scotty, I hope you're well.  You may remember that you replaced my hard drive earlier this year when it failed.  Since then, it seems that everything runs a good bit slower and I get the spinning beach ball of death quite a bit.  Maybe it's due to Time Machine, as I never used it before I crashed, but I wonder if more RAM is necessary?  I currently have 2 slots x 2GB in each (total of 4GB) with two empty slots.  I mostly use the iMac for my huge iPhoto library, iTunes and editing iMovies.  I even notice the slowness when only Mail and Safari are the only things open.  I would be interested in your thoughts.  
Thanks,
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Having 4 gigs of ram should be plenty.  That is most likely not the problem.  Time machine usually does a good job of staying out of the way by only running for a very short period of time each hour throughout the day.  If things are very slow, you may first want to check the activity monitor for possible applications that could be running without your knowledge.  That is assuming the hard drive is healthy.  I would suggest first joining me on my weekly town hall at 7pm on Mondays and I can give you a few other suggestions that we can look at.  

www.sellsconsulting.com/townhall.