Starting from about 2 months ago, I notice my 24" iMac is getting slower and slower e.g. I always see the "beach ball" even when I surf the web, and hear the HD sound. I purchased my iMac in 2008 with 4GB RAM and 500GB HD. I was thinking to redo a clean install but not sure would this help - it will take me a lot of time to re-install the OS, applications and I worry about losing my emails and photos. I use Time Machine but never try to restore the whole Mail and iPhotos, so I worry. Any advice would highly appreciated. Thanks.