Q: Macbook Unibody 2008 OS Installation Problem

What version of the operating system do you (did you) last have on the computer? If you’ve ever had 10.7 or later you should be able to boot into the recovery partition and install from there - even if your intention is to erase the hard drive and start fresh.

if you have not done so already make a backup before proceeding, or even in the event you don't proceed.

Use Time Machine to back up or restore your Mac - Apple Support

Make sure the 3rd party applications you use are compatible with 10.11, ask the developers and while 'roaring apps" can give you a decent idea it is also writhe with inaccuracies and not scrutinized to any extent of providing opinions that have not been put to the test.

Not all 2008 Mac Laptops support 10.11

verify the model you own is the model Apple claims is indeed one of the 2008 products eligible for the install of 10.11 and that you meet or exceed the "suggested" level of performance and HW specs.

OS X El Capitan - Technical Specifications

Many 2008 Mac Laptops came standard with 2GB RAM, and while Apple has stated 10.11 will run with this RAM the finding here conclusively show that a minimum of 4GB RAM is recommend for common tasks and acceptable response from the OS, otherwise it's very possible to get performance slightly above "a brick" with 2 or 3 GB RAM for even the least demanding usage.

In the event your computer is eligible for the 10.11 update and you have adequate RAM use apples recommendation for this install process and not a 3rd party

Create a bootable installer for OS X - Apple Support

It is advised you remove ALL external devices from the computer during the installation to determine if a 3rd party product is causing an issue

abhishekbisawa wrote:

 

It was Snow Leopard.

Needs to be at least Snow Leopard 10.6.8 to upgrade. Verify this was the version you were running.

Does your trackpad function normally when you are running 10.6.8?