I'm an Ubuntu user and lover. Yesterday, I decided to install Xubuntu on my sister's laptop (which had Windows 8.1 preinstalled, in UEFI mode). It's a Lenovo G400S, 4 GB of RAM, Intel i5 CPU (I don't know the exact specs, sorry). But there was an issue: I could only boot from USB in legacy mode.
Note that I didn't do it the "regular" way: instead of burning the Xubuntu ISO image to the USB drive I put a bunch of ISO images from different Linux distros inside it and installed GRUB to its MBR. To boot Xubuntu Live media (64-bit), I created a loopback device with its ISO image mounted, loaded the kernel (at /casper/vmlinuz.efi) and the initrd (at /casper/initrd.lz) and it went fine. I created a 400 GB ext4 partition and installed Xubuntu there. Everything was correct and the installation successfully finished, but it was in Legacy mode.
Now if I set the BIOS configuration to give priority to UEFI it boots directly into Windows, and if I set it to "Legacy first" it shows me the GRUB menu where I can choose Xubuntu or Windows. Xubuntu boots fine from there, but if I try to boot Windows from GRUB it throws me a fatal error and I have to hard reset.
Here are my questions:
Is there a way to convert Xubuntu to UEFI mode? Or Windows to Legacy mode? Note that I can't boot from USB in UEFI mode.
Will the computer be harmed if I keep these settings (Xubuntu Legacy mode + Windows UEFI mode)? I can live with that, but I don't know if it's harmful.