3 Beeps at startup means you have bad memory modules. Replace RAM.
Clean Install of Snow Leopard
Be sure you have backed up your files because the following procedure will remove everything from the hard drive.
1. Boot the computer using the Snow Leopard Installer Disc 1 that came
with your computer. Insert the disc into the optical drive and restart the computer.
After the chime press and hold down the "C" key. Release the key when you see
a small spinning gear appear below the dark gray Apple logo.
2. 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 the hard drive entry from the left side list (mfgr.'s ID and drive
size.) Click on the Partition tab in the DU main window. Set the number of
partitions to one (1) from the Partitions drop down menu, click on Options button
and select GUID, click on OK, then set the format type to MacOS Extended
(Journaled, if supported), then click on the Apply button.
3. When the formatting has completed quit DU and return to the installer. Proceed
with the OS X installation and follow the directions included with the installer.
4. When the installation has completed your computer will Restart into the Setup
Assistant. After you finish Setup Assistant will complete the installation after which
you will be running a fresh install of OS X. You can now begin the update process
by opening Software Update and installing all recommended updates to bring your
installation current.
5. If you are planning to sell or give your computer away, then do the following:
After you reformat your hard drive and reinstall OS X, the computer restarts to a
Welcome screen and asks you to choose a country or region. If you want to leave
the Mac in an out-of-box state, don't continue with the setup of your system. Instead,
press Command-Q to shut down the Mac. When the new owner turns on the Mac,
the Setup Assistant will guide them through the setup process.
Download and install Mac OS X 10.6.8 Update Combo v1.1.
Upgrading to El Capitan
You can upgrade to El Capitan from Lion or directly from Snow Leopard. El Capitan can be downloaded from the Mac App Store for FREE.
Upgrading to El Capitan
To upgrade to El Capitan you must have Snow Leopard 10.6.8 or Lion installed. Download El Capitan from the App Store. Sign in using your Apple ID. El Capitan is free. The file is quite large, over 5 GBs, so allow some time to download. It would be preferable to use Ethernet because it is nearly four times faster than wireless.
Macs that can be upgraded to OS X El Capitan
1. iMac (Mid 2007 or newer) - Model Identifier 7,1 or later
2. MacBook (Late 2008 Aluminum, or Early 2009 or newer) - Model Identifier 5,1 or later
3. MacBook Pro (Mid/Late 2007 or newer) - Model Identifier 3,1 or later
4. MacBook Air (Late 2008 or newer) - Model Identifier 2,1 or later
5. Mac mini (Early 2009 or newer) - Model Identifier 3,1 or later
6. Mac Pro (Early 2008 or newer) - Model Identifier 3,1 or later
7. Xserve (Early 2009) - Model Identifier 3,1 or later
To find the model identifier open System Profiler in the Utilities folder. It's displayed in the panel on the right.
Are my applications compatible?
See App Compatibility Table - RoaringApps