Error 5, Access is denied, is the most common first-run problem in Win32 Disk Imager. It almost always means Windows refused the program raw access to the drive, not that your image file is corrupt or your card is dead. The fix is usually quick, but it is worth understanding why it happens so you do not waste time re-downloading images or reformatting a healthy card.
Win32 Disk Imager v1.0.0, released 2017-03-08 and released under GPLv2, is a Windows-only tool that reads and writes whole devices sector by sector. It does not work through ordinary file operations. To open a physical drive for raw access, Windows requires elevation. If you launch the program by double-clicking its icon from a standard user account, or from a shortcut that does not request elevation, Windows blocks the device open call and the program reports Error 5. That requirement is genuine: run as administrator is not a workaround, it is how raw disk access works on Windows.
Why Error 5 happens
- Not elevated. The program was started without administrator rights, so Windows denies raw device access.
- Another program holds the drive. Explorer, an antivirus scanner, a partition tool, or another imaging tool may have the card open, which blocks exclusive access.
- Drive-letter or device confusion. The selected device is not the card, or the card was removed and reinserted and Windows reassigned it while the program still points at the old handle.
- Policy or security software. On managed or locked-down PCs, group policy or endpoint protection can block raw disk access even for administrators.
- Failing reader or card. Less commonly, a flaky reader drops the device mid-open and Windows reports the failure as an access error.
Start with the simplest explanation. Most home users hit the first item, and the fix takes seconds. Do not reformat the card, do not download a different image, and do not assume the card is broken until you have tried the steps below in order.
Fixes, cheapest and quickest first
- Close Win32 Disk Imager completely, then right-click it and choose Run as administrator. Confirm the User Account Control prompt. Re-select the drive letter and the image file, then try again. This alone resolves most Error 5 cases.
- Close everything that might touch the card. Close Explorer windows showing the card, partition managers, backup tools, and any other imaging software. If an antivirus scan is running on the removable drive, pause it for this operation.
- Remove and reinsert the card. Use Safely Remove Hardware first if Windows offers it, wait a few seconds, reinsert the card, wait for Windows to recognise it, then relaunch Win32 Disk Imager as administrator and re-select the device.
- Try a different USB port and, if possible, a different card reader. Front-panel ports and cheap readers are common failure points. A direct port on the PC, rather than a hub, is the better test.
- Check that you selected the right device. Compare the drive letter and size shown in Win32 Disk Imager with what Windows shows for the card. If the sizes do not match, stop: you may be pointing at the wrong drive, and a write to the wrong drive overwrites the entire destination.
- Test the card in another PC if you have one. If Error 5 follows the card and reader to a second PC, suspect hardware. If it works there, suspect policy or security software on the first PC.
If you are on a work or school PC, you may not be able to fix this yourself. Raw disk access can be blocked by policy even for local administrators. In that case, use a personal PC you control, or ask the administrator whether removable raw-disk access is permitted. Do not try to bypass endpoint protection; that can violate policy and will not make the write safer.
For a full walkthrough of a normal write, see how to use Win32 Disk Imager — note that the tutorial link list uses the site hub structure; the essential steps are the same: run as administrator, verify the drive letter, then write. You can also get a fresh copy from the download page and return to the troubleshooting hub for related errors.
When to stop and switch tools
Stop troubleshooting Win32 Disk Imager itself if elevation, a clean reinsert, a different port, and a different reader all still produce Error 5 on a PC you control, and the same card works in another tool. At that point the problem is likely Windows policy, a driver conflict, or a failing card, and switching to another imager will not magically grant raw access either — but testing with a second tool on a second PC will tell you whether the card itself is readable at all. If no tool on any PC can open the card, treat the card as suspect and do not keep forcing writes to it. See also Error 121 and drive letter missing for neighbouring symptoms that often share a reader or hardware cause.
FAQ
Why does Win32 Disk Imager need administrator rights?
Because writing or reading a raw disk device bypasses the normal file system. Windows only allows that level of access to an elevated process, so running without elevation produces Error 5.
I ran as administrator and still get Error 5. What next?
Close any program that may hold the drive open, including Explorer windows, antivirus scans, and disk tools, then remove and reinsert the card and try again with a different reader if the error persists.
Can Error 5 damage my SD card?
No. Error 5 means access was refused before any write started, so the card contents are not changed by the failed attempt itself.