First let me start with a little bit of logic. Apple makes THREE different types of Macs, so providing 100% compatibility is simple. There are tens of thousands (maybe even millions) of variations of PCs. There is simply no possible way Microsoft can test them all against their newest OS, nor is it fair for us to expect them to.

The Windows 10 updater seems to work remarkably well, but again, they cannot account for millions of variations. So to help the upgrade go smoothly, do the following.

Uninstall any software whose job it is to protect the computer. This includes:
1) Antivirus software (ie. AVG, Avast, McAfee, Symantec, Kaspersky, to name a few)
2) Software firewalls (ie. Comodo, ZoneAlarm)
3) Spyware programs such as Spybot Search and Destroy, Malwarebytes Antimalware and others

Uninstall your video drivers. (ATI, NVidia, Intel) Incompatible or out of date video drivers will cause the install to fail.

All of these run at the very base level of the operating system and can prevent a successful upgrade.

I hope this helps!

~~ Mac users… please refrain from telling us how Macs are better and do not require this. Linux is better than both, but it is not the operating system we are currently discussing.