Q: Please help! "This version of OS X 10.10 cannot be installed on this computer."

Repair the Hard Drive and Permissions

Boot from your Snow Leopard Installer disc. After the installer loads select your language and click on the Continue button. When the menu bar appears select Disk Utility from the Utilities menu. After DU loads select your hard drive entry (mfgr.'s ID and drive size) from the the left side list.  In the DU status area you will see an entry for the S.M.A.R.T. status of the hard drive.  If it does not say "Verified" then the hard drive is failing or failed. (SMART status is not reported on external Firewire or USB drives.) If the drive is "Verified" then select your OS X volume from the list on the left (sub-entry below the drive entry,) click on the First Aid tab, then click on the Repair Disk button. If DU reports any errors that have been fixed, then re-run Repair Disk until no errors are reported. If no errors are reported click on the Repair Permissions button. Wait until the operation completes, then quit DU and return to the installer.

If DU reports errors it cannot fix, then you will need Disk Warrior and/or Tech Tool Pro to repair the drive. If you don't have either of them or if neither of them can fix the drive, then you will need to reformat the drive and reinstall OS X.

Now try again to download. Be sure you are downloading the full installer - 5.3 GB file - and not an updater.

In addition to Kappy's advice, open Disk Utility and click on the physical drive icon at the far left. At the lower right, what does it say the Partition Map Scheme is? If it's Apple Partition Map, that's why you can't install Yosemite (or any version of OS X from Lion on up). It must be GUID.

Click on the Apple Menu's, "About This Mac." Open the system profiler and verify that you have at least a MacPro3,1 or higher. The Early 2008 Mac Pro is the 3,1 model, so perhaps you don't have an Early 2008 model.

The year represents the year the model was introduced, not when you purchased it.

Sir_Maksuz wrote:

 

Correction: Mac Pro (early 2008), Mac OS X (10.6.8)

Can you check your Mac Model Identifier. Is it Mac Pro 3.1 or 2.1? How to identify Mac Pro models - Apple Support

If the named computer is a Mac Pro (tower) then it should be able to use up to

32GB of RAM installed across several memory upgrade slots, and also have

no issue running OS X 10.10 Yosemite. An item of historical note for that model

is there had been a Firmware Update for it some time ago, that may have been

required to be installed prior to later OS X versions and support function.

•Mac Pro (Early 2008)

Introduced    January 2008

Discontinued    March 2009

Model Identifier    MacPro3,1

Model Number    A1186

EMC    2180

Order Number    MA970LL/A (two 2.8 GHz)

Maximum Memory:    32 GB (none affixed permanent to logic board)

Memory Slots:    8 - 240-pin PC2-6400 (800MHz) DDR2 ECC fully-buffered DIMM (FB-DIMM) (matched pairs)

[from http://mactracker.ca download database app for model info given]

•However, if the computer is a notebook model MacBook/Pro, that is quite a different

animal and requires slightly adjusted care and feeding intervals. And an early model

may not be able to run Yosemite if the hardware isn't capable. Mountain Lion?

Please supply more build model. You may have to reset SMC and perhaps NVRAM

to be sure the computer is OK; and perhaps perform a hardware test.

Good luck & happy computing!

The OP needs to confirm that he has a 3.1.

And that it is a tower, etc...

When I started my reply, nobody had posted any thing.

MacPro1,1. That's the reason. That model doesn't support anything newer than Lion, 10.7.x.

Then the message from Apple is correct. If Apple had used yearly naming conventions back then, it would have been called a Late 2006 Mac Pro.

your computer is a 2006 model, the 3,1 was the 2008's but Yosemite with 3GB RAM would be shooting yourself in the foot to run faster.

I would recommend adding more RAM. Your Max would be 32 Gigs, but 8 Gigs would be a good choice. I'd stick with Snow Leopard, unless Lion was needed for some reason. Lion can be purchased here: http://store.apple.com/us/product/D6106Z/A/os-x-lion

You should backup your system beforehand, to en external drive. I'd recommend using a cloning software, i.e., Carbon Copy Cloner, in lieu of Time Machine, because you would be able to boot from a cloned drive.

Glad you were able to correctly identify the computer model & build specification.

This helps those who have access to a larger choice of online or offline database

do minor research; with hundreds of model build year model variants out there...

http://www.everymac.com/systems/apple/mac_pro/index-macpro.html

Snow Leopard is probably the best if not one of the best Apple produced, and if

you have several great older applications that run on there, stay with it. Be sure

to obtain quality RAM upgrade chips and make a backup of your files in external

or separate storage drive location just in case the hard drive takes a dive.

In any event...

Good luck & happy computing!