I need to install Windows 7 on my ASUS T100TA which has a 32-bit EFI without Legacy Boot option. Windows 8.1 is very lagging, so why don't try install Windows 7?

First, I prepared 32-bit Windows 7 install USB, entered into BIOS, disabled Secure Boot, but the USb didn't boot.

I also tried other way: Created Windows PE 5.1 bootable USB with extracted Windows 7 ISO which successfully booted. I then opened Command Prompt and ran Windows 7 setup, accepted license, selected "Custom install", deleted ALL partitions from 32GB Flash drive, created new partition, but it can't install Windows 7 there (missing Intel SD Host Controller driver).

Can anybody help me unlock the Legacy Boot option or give me the BIOS-emulation bootloader?

  • 1
    AFAIK, there's no way to add BIOS/CSM/legacy support to a firmware that lacks that support, short of replacing the firmware. Even if you did that, it wouldn't help with driver support issues, which is your problem. To that end, you should check with ASUS, or with whoever made the controller for your "disk" (really flash storage) device. Even if you get this support, AFAIK Windows 7 won't work well on a tablet because of user interface issues. Personally, I'd stick with Windows 8, return the computer for a refund/replacement, or maybe look into running Android on it.
    – Rod Smith
    Oct 10 '15 at 16:48
  • I did clean Windows 8.1 install (not recovery), installed all drivers from ASUS website, installed Office, Windows updates and Chrome, It works well (better than ASUS pre-installed Windows copy), yesterday I tried install Ubuntu 15.10, but no success (booted into "Try Ubuntu", updated grub via terminal, started setup, but after create user account setup hang, after 20 minutes I got "read error" message.
    – DJ Vozny
    Oct 10 '15 at 17:27

Windows 7 needs BIOS INT10 to boot, in turn requiring CSM.

So, your only choice if you don't want Windows 8/10 is Linux. No need to even disable Secure Boot thanks to the Linux foundation shim most distros ship with.

There are also reported hacks to make 64 bit OS load.

EDIT: it turns actually out there exists hacks for booting without CSM!
EDIT2: UefiSeven has you covered completely now.

EDIT3: duh, the bay trail tablet has a 32-bit firmware, right. And that means W7 requires some extra meddling to work.

  • I could be reading wrong, but this seems to contradict information given in another answer, which suggests you can indeed install Windows 7 64 bit. Can you elaborate?
    – bertieb
    Feb 19 '17 at 21:39
  • Other answers say that if you have CSM/legacy it will work. I'm just observing this simply isn't here (bar.. I dunno, you rewriting the bios or something) and ultimately summing up the alternatives then.
    – mirh
    Feb 19 '17 at 23:48
  • Okay fair enough, I didn't see a mention of CSM in Hennes' answer. I'm not sure "install Linux" answers the question of "how to install Windows 7?"! However, if there are 'reported hacks', they should be summarised here in case the link goes dead :)
    – bertieb
    Feb 20 '17 at 0:05
  • "No you can't" technically is an answer. Then actually nothing is impossible, but I think I'd go OT then. And same into mentioning hacks OP may or may not be interested in (after all, I'm just talking after an hypothesis I made of his needs). They are archived on wayback machine anyway.
    – mirh
    Feb 20 '17 at 13:16
  • 1
    You make an interesting point, so I asked a meta question about it :)
    – bertieb
    Feb 20 '17 at 20:37

You can't.

I have a ASUS M81C which is the same situation as yours, after months research, try and fails, I gave up.

The reason why it's impossible is, Windows 7 only have partial UEFI support on 64 bit version(need CSM), and have no UEFI support on 32 bit. Also, it's nearly impossible to modify the BIOS to add CSM or even legacy mode, you cannot unlock it because it non-exist on your system. And about chain loading, AFAIK, it's not possible on Windows.

If you think about Linux, yes you can have a 64 bit Linux OS on it, but it needs a lot of tweaking and it's buggy.

So we have to live with windows 8 or windows 10, and 32 bit only.


How I can install Windows 7

First of all, it depends on how you want to install it.

Classic/Legacy mode:

  • You need an option in the UEFI firmware do disable the dreaded secure boot.
  • You would need a EFI firmware which emulates int 10, else the installation crashes (sometimes available as 'windows 7 mode'.)
  • You need a USB pendrive with a valid bootsector (or a DVD).

EFI mode

  • You need windows 7 64 bit (not 32 bits, then again, nobody used a 32 bit OS anymore).

  • You need a windows 7 DVD, or a pendrive formatted in FAT32 (not NTFS!), and with avalid /boot/bootx64.EFI file (which you would need to move manually).

  • And you still need an EFI firmware with a 'windows 7 mode' to emulate or capture int10.

Obviously you will also need relevant drivers. Drivers are usually ignore since windows 7 was great with build-in drivers. But for a modern laptop, especially those with USB3 ports, you will need additional drivers for things like USB, thunderbolt etc etc.

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