dim — Disk Image Mounter

Double-click an image, get a real DVD drive. No driver. No admin. 340 KB.

Quick start · Formats · Shortcuts · How it works · Limits · FAQ · Build · AI disclosure

dim is a tiny Windows 10/11 app that mounts disc images as real optical drives, using the same virtual-disk API Windows itself uses for ISO files. Drop an image on the window and a new drive letter appears in Explorer. Close dim, or let it crash, and the drive disappears cleanly. Nothing is installed and nothing is left behind.

Why dim

No driver	Mounts through the native virtdisk API. No kernel driver, no reboot, no signing prompt.
No admin	Runs as a normal user. The manifest is asInvoker.
Tiny	About 340 KB exe, about 11 MB of RAM, 0% CPU when idle. No runtime, no UI framework.
Self-cleaning	A mount lives only while dim runs. If dim exits or crashes, Windows detaches every drive.
Many formats	ISO, CUE/BIN, IMG, RAW, NRG, plus basic MDS/MDF and CCD/IMG. Detected by content, not by extension.

Quick start

1. Download dim.exe from the latest release.
2. Run it. No installer.
3. Mount an image: drag it onto the window, press Ctrl+O, or click Mount….

Double-click a row to open the new drive in Explorer. Select it and press Del to unmount.

Tip

Closing the window keeps dim in the tray. Start it hidden with dim.exe --tray; a balloon announces mounts made while it is hidden. Quit from the tray menu asks first, then unmounts everything.

Windows warns about the file?

The exe is not code-signed, so SmartScreen may warn on first run. Click More info, then Run anyway. You can compare the file with checksums.txt from the release page (Get-FileHash dim.exe).

Supported formats

Format	Support	How
ISO	✅	Mounted directly. CD, DVD and Blu-ray (UDF) images, no conversion.
CUE / BIN	✅	Reads the .cue, extracts the first data track.
IMG / RAW	✅	Any extension. Detected by the CD sync pattern (2352 or 2448 bytes/sector).
NRG (Nero)	✅	Reads the NER5/NERO footer and the track chunks.
MDS / MDF (Alcohol)	Basic	Metadata is not parsed. The sibling .mdf is read as a raw image.
CCD / IMG (CloneCD)	Basic	Metadata is not parsed. The sibling .img is read as a raw image.

Note

Everything except ISO is first extracted to %TEMP%\dim\*.iso, so you need free space equal to the image size. The temp file is deleted on unmount, and leftovers from a crash are removed at the next start.

Shortcuts and command line

Action	How
Mount an image	Drag and drop, Ctrl+O, or Mount…
Open the drive	Double-click a row or press Enter
Unmount	Del or Unmount
Recent images	The arrow on Mount… (last 10, also in the tray menu)
More actions	Right-click a row: open, show in Explorer, copy path
Mount from a terminal	dim.exe "D:\games\disc.cue" "D:\tools\setup.iso"
Start hidden	dim.exe --tray

Launching dim again hands your paths to the running instance and exits, so there is only ever one window. The window remembers its position and size.

How it works

 .iso ─────────────────────────────────────────────┐
                                                   ▼
 .cue .bin .img .nrg ─▶ prepare() ─▶ extract() ─▶ temp .iso ─▶ AttachVirtualDisk ─▶ E:\
 .mds .ccd .raw          (sniff)    (1 MiB stream,                (read-only, no       real optical
                                     cancellable)                  PERMANENT_LIFETIME)  drive in Explorer

• The drive exists only while dim holds the virtual-disk handle. Closing the handle detaches it.
• The drive letter is assigned asynchronously by Windows; dim keeps polling until it shows up.
• Ejecting from Explorer is detected, and the entry is removed from the list.

The full design notes live in AGENTS.md.

Limits

• Audio tracks are not emulated. Mode 2 Form 2 data (VCD/PS1 streams) comes out wrong.
• MDS/MDF and CCD/IMG work only for a single simple data track starting at LBA 0.
• Compressed formats (CSO, CHD, ISZ, DAA, ECM) are unsupported.
• "Sparse" ISOs (common from torrents) cannot be mounted by Windows; dim shows the fsutil sparse setflag fix.
• Windows 10/11 x64 only.

FAQ

Why does it not need administrator rights?

Attaching a read-only ISO through virtdisk works for a standard user. dim never asks for elevation.

Where do my mounts go when I close the window?

Nowhere: closing the window only hides dim in the tray, and your drives stay mounted. They are detached when you choose Quit or when the process ends.

Why is a drive letter missing right after mounting?

Windows assigns it a moment after the attach call. dim fills it in as soon as it appears (up to about a minute).

Build from source

Needs Rust 1.99 (edition 2024) and the MSVC toolchain.

cargo build --release   # -> target/release/dim.exe
cargo test
cargo clippy --release --all-targets -- -D warnings

Close any running dim.exe before rebuilding, because Windows locks the binary.

assets/   icon, manifest, resource script, logo SVG
docs/     images used by this README
src/
├─ main.rs      window, tray, list view, message loop
├─ convert.rs   format detection and extraction to ISO
├─ vdisk.rs     virtdisk attach/detach, drive letter lookup
└─ store.rs     recent list and window placement

AI coding agents and contributors: start with AGENTS.md.

AI disclosure

Generative AI wrote most of this project. The Rust code, tests, documentation and CI workflows were produced with Claude Code (Anthropic). The developer set the goals and design decisions, carefully reviewed the generated code, tested the app on Windows, and is responsible for the result. Bugs are possible: please open an issue.

License

MIT © 2026 Glauber Lima