The update stopped with an error and your heart skipped - a drive full of ISOs, gone? Almost certainly not. Here is what a failed update really means and the recovery order that protects your files at every step.
An error message during a Ventoy update feels like a disaster, but the layout of the drive is on your side: the update writes only to the small boot partition, so a failed update is a boot problem, not a data problem. Work through this page calmly and in order. The single rule above all others: do not click Install in a panic - it is the one action that turns a small hiccup into real data loss.
An update writes only a few megabytes to the boot partition. When it reports failure, the usual causes are ordinary: a File Explorer window or another program was holding the drive open, the USB connection dropped for a moment, antivirus software intervened, or the pen drive itself is wearing out. In almost every case the data partition - your ISOs, your ventoy folder - was never part of the failed write and is completely fine. The drive may temporarily refuse to boot while its boot files are half-written, but a boot problem is not a data problem.
Ventoy2Disk.exe as administrator, select the drive, confirm the version lines, and click Update again. A half-written boot partition is exactly what a successful retry repairsThis is the happiest failure of all: your data is safe, only the boot side is damaged. First try one more clean Update as above. If Update keeps failing at the same point, copy all your files - ISOs and the ventoy folder - onto the PC, and only then use Install to rebuild the drive from scratch and copy everything back. Because you copied the files off first, even this worst path loses nothing.
If updates fail repeatedly on different PCs, or files on the drive start showing errors, stop blaming the software: the pen drive is telling you it is dying - or that it was a fake-capacity drive all along. Move your ISO collection to a known-good drive, keep a second ready Ventoy drive in the bag from now on, and retire the suspect. A bootable toolkit drive is emergency equipment; it has to be boring and reliable.
Watch the video's update once, and keep this recovery order in mind - you will probably never need it, and that is the point.
Watch Full VideoAlmost certainly not. Update writes only to the small boot partition; the data partition with your ISOs is not part of that write. Open the drive in File Explorer - in nearly every case your files are listed normally, and a clean retry of Update fixes the boot side.
Something holding the drive open - an Explorer window, a file copy, or antivirus software - or an unstable USB connection through a hub or loose port. Close everything, reconnect the drive directly to the PC, run Ventoy2Disk as administrator and retry Update.
Treat the pen drive itself as the problem - it may be wearing out or a fake-capacity drive. Copy your ISOs and the ventoy folder to the PC, move to a known-good drive, and retire the suspect one. Do not keep repairing a drive you cannot trust.