Im running Arch Linux and I needed windows to run a game that just didn't want to run properly in wine. So I installed windows 8.1 without any problems and Ive always been told that installing windows after installing linux is not a good idea as it will break grub. However, I was still able to completely boot into linux again(with a small hiccup but a second reboot went smoothly. Why would this be and is there anything I should check just to make sure to check just in case?
It really depends on how you installed Windows. If you installed it to a different HDD than your Linux install was on, then Windows wouldn't have touched GRUB because it is on a different disk. If Windows was installed on a different partition of the same drive as Linux, then I don't know why it didn't overwrite the boot sector, it should have. Regardless, you will not have a Windows boot option in your GRUB menu if you install Windows after installing Linux. In order to update the GRUB menu, you need to run the update-grub command. Google it to make sure you do it correctly for Arch, I have never used Arch before.
I don't think arch will effect anything. Grub is completey separate.
update-grub only works on Ubuntu (and maybe some other distros), not Arch. Arch has a different command (it's "grub-mkconfig -o /boot/grub/grub.cfg"). That's the wrong command anyway though. You need to run grub-install to re-install GRUB to the boot sector then you have to run that command so GRUB will recognize Windows. This is for legacy BIOS. I don't know much about UEFI, so I don't know how it works in that situation.
EDIT: I misunderstood your original post. What you said about the update-grub command was correct, however it still stands that command does not work for Arch. Instead you should use the command I mentioned above. After a Windows install that does bork GRUB, you can very easily fix it by using the Arch Live CD, arch-chrooting into your system, and then running grub-install. That's what I meant.
Ahh, good to know. This is why I was directing them to the Google to make sure they got the correct information. Thanks for clearing that up.
I already ran the mkconfig for grub to find windows. I was expecting for the worse and have to boot off a liveCD and I didn't see any posts on any forums saying that there is a chance it wouldn't overwright the boot sector.
Was Windows installed on another drive, or the same one partitioned? Also, are you using UEFI or Legacy BIOS? Again, I don't know much about UEFI, but I think it stores boot data on a separate partition instead of the MBR, so if Windows couldn't see that partition, or thought it was something else, it wouldn't overwrite it. If it was on a different disk, that might explain it, but when I have installed Windows in the past, it has destroyed the MBR on every drive in the machine. That's why you should disconnect every drive except the one you are installing Windows on until you get it installed.
Windows installation did not kill GRUB!
Better try again, then!