How do I get Windows 10 installed on my macbook pro (late 2008)
How to install Windows without using the BootCamp Assistant.


Download and copy the Boot Camp Support Software to a flash drive.
You will need this later.
You need to create a "MS-DOS (FAT)" formatted partition. 

One way would be during a clean install. Use the Disk Utility to
create a two partitions. The  first would be "Mac OS Extended
(Journaled)" for OS X and the second would be "MS-DOS (FAT)"
formatted for Windows. Install OS X to the first partition. I would
avoid using Core Storage.

The second way would be to create a single "Mac OS Extended
(Journaled)" partition and install OS X. Again, avoid using Core
Storage. Once installed, you should be able to use the Disk Utility
to shrink this partition and add a "MS-DOS (FAT)" formatted
partition for Windows.
Bless the Windows partition. Using the Disk Utility application,
highlight the "MS-DOS (FAT)" formatted partition and click the Info
button. Note the Disk Identifier. It usually is disk0s4. To install
Windows, the last digit can not be greater than 4. In a Terminal
application window, enter the following command. 

sudo bless --device /dev/disk0s4 --setBoot --legacy


Here is assumed disk0s4 is the correct Disk Identifier.
Set the active MBR partition. From a Terminal application window
enter the following.

sudo fdisk -e /dev/disk0
flag 4
quit
yes


Here 4 was used because it was the last digit of the Disk
Identifier. Below is an example of me entering the above commands.

Steelhead:~ davidanderson$ sudo fdisk -e /dev/disk0
Password:
fdisk: could not open MBR file /usr/standalone/i386/boot0: No such file or directory
Enter 'help' for information
fdisk: 1&gt; flag 4
Partition 4 marked active.
fdisk:*1&gt; quit
Writing current MBR to disk.
Device could not be accessed exclusively.
A reboot will be needed for changes to take effect. OK? [n] yes
Steelhead:~ davidanderson$ 

Install Windows. Insert the Windows DVD and restart the computer.
Hold down either Option key during restart. Choose the DVD when the
icons appear. If you have more than one DVD icon, there may be a
problem with the DVD. In this case, see the note below.
After the installation of Windows is complete, insert the flash
drive and install the Boot Camp Support Software.


This was done from my memory. If you have a problem, let me know.

Note: More Than One DVD Icon

When trying to boot to the Window installation, DVD you may get two DVD icons to choose from. They are usually labeled "Windows" and "EFI Boot". The correct choice is "Windows". This may lead to the following message being displayed.

       1.

       2.
Select CD-ROM Boot Type :


I found this to be true using a DVD burned from the  "Windows10_InsiderPreview_x64_EN-US_10074.iso". The message has also occurred using certain Windows 7, 8 and 8.1 installation DVD's. The problem is the DVD and not with the steps given in this answer. The solution is to remove the "EFI Boot" method from the DVD or iso image. The procedure is given at “Select CD-ROM Boot Type:” error during Windows install.