Q: Can someone help me fix my mac?

Hi there

Mac OS (as it's now called) needs the file extension to understand how to open and run files. By deleting the extensions, it's likely the the OS didn't know what to do with the files.

What files did you delete the extensions of?

Just goes to show a little bit of knowledge can be dangerous and destructive, yes?

You should never, EVER play around in the OS X system folder when clearly you didn't know what you were doing!

Have you EVER backed up the data on your Mac prior to your issues?

So, never had a backup of your computer data.

Every computer user should ALWAYS have, AT THE VERY LEAST, one external drive to regularly backup your personal data to.

Either an external hard drive and/or large capacity USB flash stick style drives for data backup. Something to save your data to that is just not single internal hard drive on your computer.

What year and model iMac do you own?

To find out info about your system,
Click on the Apple symbol in the upper left of the OS X main menu bar. A drop down menu appears.
Click About this Mac. A smaller popup window appears. This gives you basic info like what version of OS X your iMac is running, the speed of your iMac's CPU and how much RAM is installed.
Click on the button that says More Info.
A larger window appears giving you a complete overview of your iMac's hardware specs.
Highlight all of this info and copy/paste all of this into another reply to this post, editing out your iMac's serial number before actually posting the reply.
This will tell us everything about your iMac so we may begin to help with your iMac issues.

Did this iMac originally have OS X 10.9.5 Mavericks installed on it or did you install this OS X upgrade, yourself?

Do you have important personal data that we need to save?

How tech/Mac saavy are you?

I am afraid of going down the road we need to go if you are not comfortable dealing with technology and technology issues.

I am basically advocating/ advising a backup of your current iMac system (using the purchase of a fast connected, large capacity hard drive using different software tools)and doing a complete wipe of your current system and reinstall everything new and manually moving your actual saved data back to your newly clean installed system.

This invovles the purchase of an external hard and purchase of some additional software.

There is a significant amount of stuff to be done.

Is this something you think you can handle as I really do not want to waste my time spelling out procedures if you feel this could be beyond your tech skill level to handle.

You can easily transfer whatever important files you have on your iMac to whatever USB flash drive/s you have.

Plug in your USB drive/s into one of the USB ports on the back of your iMac.

The icon of the drive will appear in the Finder.

Double click the drive icon to open a window into the drive.

Then, It's simple drag and drop files into the drives open window.

You can drag and drop entire folders or groups of files or induvidual files one at a time, if you have to.

Just copy whatever important personal files you have on your iMac to those thumb drives before doing anything else.

You will need another USB flash drive to use to install a bootable version of  OS X Mavericks on to first (the USB drive needs to be 8 GBs in size or greater) and you will need to use OS X Disk Utility to reformat the drive as OS X Extended (journaled) with GUID partition scheme.r

Then, folllow the instructions in these links.

http://osxdaily.com/2013/10/26/clean-install-os-x-mavericks/

http://osxdaily.com/2013/10/23/create-os-x-mavericks-install-drive/

You will have to reinstall ALL of your third party software from scratch.

Never, EVER trash the OS X system extensions folder ever, again!!!

You totally bodge up your iMac when you carelessly did this and created a lot more work for yourself than was ever needed.

Good Luck to you.

If you did not Gank your iMac up you could Google this, too! 

Bad, bad, naughty mouse finger!! Okay, I'll stop with the abuse. You learnt a lesson, huh?

GUID Partition Table (GPT) is a standard for the layout of the partition table on a physical storage device, such as a hard disk drive or solid-state drive, using globally unique identifiers (GUID). Although it forms a part of the Unified Extensible Firmware Interface (UEFI) standard (Unified EFI Forum proposed replacement for the PC BIOS), it is also used on some BIOS systems because of the limitations of master boot record (MBR) partition tables, which use 32 bits for storing logical block addresses(LBA) and size information on a traditionally 512 byte disk sector.

How to restore 2012 imac to factory settings

How to reinstall OS X on your Mac - Apple Support

Seriously, now is not the time to be worried about what GUID means. Just select it in Disk Utility. Every OS needs to be setup on a drive that has the appropriate Partition Map and format for it to be installed and read and write to the drive in logical cylinders, tracks and sectors. This is not the time to get into that. I provided you with the above links and you have Mr. MichelPM's links as well. Last "but" chewin'. Don't go playing around with the System unless you want to go through this again! 

You will erase your APPLE HDD and create 1 single Partition (GPT) Mac OS Extended (Journaled) name it Macintosh HD. You will have to follow Apple's Internet Recovery procedure to restore to Mavericks ( out of box ) condition. As the old song goes "Pick yourself up and dust yourself off and start all over again"

You will have to do the Mac OS X upgrades from Mavericks, I'm afraid. That may be the issue for some Apps not compatible.

Hope this helps!

Cheers!!

Please make sure you read the about all the preparation and procedures before updating OS X. There is a rhyme to reason. Make sure Mavericks is configured and updates have been installed, including downloading your Apps in Purchases from the App Store. The Apple ID you used to set up and register your Mac needs to be handy for smooth operation.

Cheers!!

Formatting drives for OS X.

http://pondini.org/OSX/DU1.html