Hi all. My 500GB Yosemite loaded HD crapped out about two weeks ago. (I think resulting from me accidently letting my laptop slowly drop to the floor from my lap on the couch ) It worked for a while after that, but I got the gradual beach-balls then resulting to a crawl with anything I tried to do. I eventually formatted the hard drive and installed Snow Leopard on it - clean install. It seemed to work faster since it was an older OSX, but my thoughts and hopes of thinking that Yosemite was making my MBP extremely slow due it being an older MBP were quickly destroyed. I tried to repair permissions in Disk Utility, but received some errors in red that I can't remember at this point in time. All I remember was that the my hard drive label on the left side column was red also. I then rebooted and got the blank gray screen. After many reboots and attempts to boot into safe mode, I got the do not enter type sign screen... then the blank folder image upon boot screen. I did my research and I tried and ordered a new SATA cable, as I've read that those have a high failure rate on these models. I replaced the SATA cable and the drive would still not boot. It still wouldn't even boot into safe mode. I booted from my Snow Leopard CD and then it wouldn't even recognize/mount the hard drive when I went into Disk Utility. When it got to this point, I couldn't even attempt to try and use DiskWarrior. Furthermore, I didn't have an external case to try and test the drive that way either. So after many nights of frustration, I took the plunge and bought a new 512GB Crucial SSD for about $230and received it a few days ago. I installed Snow Leopard clean and copied all my important files over to my SSD from an external HD that I have. I'm already impressed at how much snappier my computer feels with the SSD. Anyway, I'm trying to make my MBP last as long as I can and enjoy using it at the same time. I'm presently running Snow Leopard and was wondering what you guys thought the best OSX would be for me to have on a machine of these specs? Also, with this being said, is there anything else I can do to upgrade my laptop to boost performance? 15" MacBook Pro - 2009 model Core 2 Duo 2.53 8GB Ram Thanks all.