Your only PC is dead, Windows will not start, and there is no second computer in the house. Your phone can still save the day — with an OTG adapter it can write a proper bootable USB that the dead PC will boot from. Here is the complete method, with its honest limits.
Every bootable USB guide assumes you have a working PC to make the USB on. In a real emergency that is exactly what you do not have. The good news: a modern Android phone is a small computer with a USB port, and with USB OTG it can write a bootable pen drive almost the way a PC does. This guide covers the whole job — what you need, how to get the ISO file, the two ways of writing it, the erase warning you must not skip, and how to boot the dead PC afterwards. The exact app used on screen is shown in the video above; this page explains the method so you understand every step whichever writer app you use.
This trick is for one situation: the PC cannot boot, and no working PC is available — at night, in a small office, at a site, or when the only other machine is far away. If a working PC exists, use it instead; writing on a PC with Rufus or Ventoy is faster and less fiddly. The phone route is the rescue rope, not the daily road. It also only works on Android. An iPhone cannot write a bootable USB this way — iOS does not give apps this kind of raw access to a USB drive.
Download the ISO you need — a Windows installer, a Linux installer, or a rescue image — from the official source only: Microsoft for Windows, the distribution's own site for Linux. Expect roughly 5 to 6 GB for a Windows 11 ISO (approximate — builds change), so Wi-Fi is strongly preferred over mobile data. Keep the download unbroken; a half-finished 6 GB file is the most common cause of a USB that refuses to boot. If the publisher shows a SHA-256 checksum on the download page, a checksum app on the phone can verify your file matches it exactly. There is a full case guide on this page set about downloading the ISO safely.
Writer apps work in two shapes. A Ventoy-style installer app installs the Ventoy boot system onto the pen drive once; afterwards you simply copy ISO files onto the drive like normal files, and at boot time a menu lets you pick which ISO to start. A direct ISO writer app writes one ISO image raw onto the drive — one image per drive, and changing it means writing again from zero. For a one-time rescue, direct writing is simpler. For a drive you will reuse, Ventoy is the better investment. Both shapes fully erase the drive first — the next step is not optional reading.
Plug the USB into the dead PC, switch it on, and tap its boot menu key — commonly F12 on Dell and Lenovo, F9 on HP, F8 on ASUS, F11 on MSI (the brand's manual is the authority). Choose the UEFI entry for the USB drive. Official Windows and Ubuntu images are digitally signed, so they boot with Secure Boot on. A Ventoy drive may ask for a one-time key enrolment on some PCs, or Secure Boot may need to be paused in the BIOS for that machine — the video and the boot case guide in this set walk through it.
Three honest warnings. First, not every Android phone supports USB OTG — some budget models cannot power or even see a USB drive; test yours with any pen drive before the emergency. Second, phone writing is slower and easier to interrupt than a PC — a loose adapter or a battery-saver killing the app mid-write leaves a half-written drive that must be written again. Third, this method makes an installer or rescue USB; it does not fix the PC by itself. The real fix — repair, reinstall, data rescue — starts after the PC boots. Technicians who do this often keep a ready-made Ventoy USB in a drawer; that prepared drive will always beat an emergency phone write, as the last case guide here explains.
The video shows the complete live process on a real phone — the app, the OTG connection, the write, and the dead PC booting from the finished USB.
▶️ Watch Full VideoYes. The common writer apps for this job — both the Ventoy-style installers and the direct ISO writers — work on a normal, non-rooted Android phone. They use the standard USB permission Android shows you, nothing more.
No. iOS does not let apps write a bootable image to a USB drive, so this emergency method is Android only. With only an iPhone available, the honest fallback is any working PC — a neighbour's, an office machine, or a cyber café PC.
The usual cause is that the phone does not support USB OTG, or the adapter is charge-only. Test the same adapter with a USB mouse or a different drive. If nothing is ever detected, this phone cannot do the job — the failure case guide in this set lists the fallbacks.