You know if you will do some research you will find that Mackeeper has implemented tons of marketing strategies. For Instance, they have huge fan following on facebook.com. Their site is well-designed with customer feedback & testimonials. However, when it comes to software they will force you download & install via several unethical channels like ads etc. If you google 'MACKEEPER' and you will mostly find negative search results ranking.
Once you get disk utility report (which Dan suggested) it will let you know if drive is OK. Meanwhile you can also check if drive is not fragmented. Yes it can happen to a Mac system You can free download defrag software to check if HDD is fragmented. Though chances are less, fragmentation may also cause Mac to slow down, particularly with older drive running some big applications. Chrome may also have corrupt preference files which you can delete by navigation through its folder.
Well I would prefer running Stellar Drive Defrag since Prosoft is much costlier and it is a data recovery app. On the other side Stellar Mac Drive Defrag is dedicated tool to optimize & defrag hard drive.
"I am skeptical if data went to trash. From an external source the data is deleted without going to trash. It is always recommended to backup HDD data before partitioning it as segregating the drive shifts HDD blocks from on to another place. Get a copy of data recovery software. I would recommended either of the below: http://www.stellarinfo.com/mac-osx-recovery.php http://www.cleverfiles.com/ Regards"
This is really technical and won't be fixed with some general tips or tricks. Your Mac fails to read it that means it underwent some corruption that OS X is unable to get it. Since PC is a different platform than OS X, it somehow seems to read the disk, that too incorrectly. You must first get this disk checked with a HDD repair software. If it got a directory structure corruption then it might get fixed with the help of partition repair software such as Disk Warrior (http://www.alsoft.com/diskwarrior/). You can also try Stellar Volume Repair (http://www.stellarphoenixrecovery.com/so...-volume-repair.php). Both the repair software are good choices for directory structure replacement. Though, Stellar Volume Repair is much cheaper than Disk Warrior and is equally skilful.
If you want to try data recovery apps for free then you have plenty of options available for Mac. Go for Stellar file repair http://www.stellarinfo.com/mac-osx-recovery.php, try disk drill for Mac http://www.cleverfiles.com and Softtote Mac recovery http://www.softtote.com . Trying more than 1 tool will help you evaluate & compare the recovery performances. Go for the one which gives back maximum recovery figures. Get back to me for more info.