Error -3 is an Unsupported platform detected error. It usually determines that the Mac does not support 64-bit software. Upgrade your processor (iMac/Mac mini) to a 64-bit capable processor and restart MacPostFactor. However if you have a MacBook 2,1 or newer, this could well be a partition issue.
1 Open Disk Utility, located in /Applications/Utilities/ .
2 Select the disk where the volume you intend to upgrade resides. This usually starts with a number representing the total size of the disk.
3. Click the Partition tab.
4. Click and drag the resize corner of your intended install partition to make the size slightly smaller.
The blue portion represents used data space. The partition only needs to be approximately 5GB or 6GB smaller than it was before resizing but it needs to be larger than the blue portion.
5. Click Apply.
6. When the partition resizing is complete, quit Disk Utility and install MacPostFactor.
7. After the OS X installation is complete, you can use Disk Utility to resize the partition back to its original size by dragging the resize corner to make the partition as large as it was before.