dual boot - How do I reinstall ubuntu from 32 bit to 64 bit? - Ask Ubuntu

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what did in mess

i'm new ubuntu convert , tried dual booting lenovo ideapad 100 ubuntu gnome , windows 10. turns out failed, installed ubuntu in legacy mode because way laptop let me. didn't delete windows partitions windows 10 can't boot now, guess need reinstall in legacy mode (how do that? being able use old partitions great too).

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installing ubuntu 32 bit 64 bit

another problem have installed ubuntu gnome 32 bit version, thinking couldn't use 64 bit version called amd64, because have intel processor( later did realize can, , should've installed that). looked around , found can somehow upgrade in terminal, reinstalling better , less hassle. being clean install don't mind reinstalling, how supposed that? ( + i've flashed needed 64 bit image on usb)

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additional

here's boot info if helps: http://paste2.org/a0zx9f7m

chances windows installation intact , bootable not booting because you've activated firmware's compatibility support module (csm), aka "bios mode" or "legacy mode" support. if i'm right, de-activating csm should fix windows boot problem. details of how vary 1 computer another, can't provide step-by-step instructions.

if can windows booting in efi mode again, suggest try again install 64-bit ubuntu in efi mode. see this page of mine background information on why using csm bad. page includes a section on creating efi-bootable usb drives, seems single biggest hurdle people face when trying install ubuntu in efi mode. note installing 64-bit ubuntu in efi mode fresh installation, old 32-bit installation wiped out, including user data. if you've stored files want keep, sure them external media. also, may need use "something else" installation option, described in this question , answers. if use 1 of more automated settings, may end both old , new installations living side-by-side, old 1 useless, or @ least redundant.