I installed and ran Ubuntu on the laptop until it's novelty wore off and now I want Manjaro on it.
I burnt the ISO with unetbootin and got it to boot in legacy mode. After the install completed I rebooted into the hard disk and all I get is grub rescue: unknown filesystem. I try to reboot into the usb and now the usb won't boot. The Windows 8.1 partition still is working fine.
Any help would be great.
You have a few options.
1. Find the partition with grub recovery and boot into Manjaro.
This webpage shows the basics --> Linky
2. Chroot from any linux live disk/media and recheck grub with a few extra flags if a simple install won't work.
Arch wiki --> Linky
eg; sudo grub-install --recheck --disk-module=native /dev/sdx
don't foget the grub config tool grub-mkconfig -o /boot/grub/grub.cfg
3. Not recommended but use BCDBoot in windows.