A critical Windows 11 bug has locked some users out of the C: drive, Microsoft admits — here's what you can do if you're affected

• A critical Windows 11 bug is affecting C: drive access
• It seems to be tied to Samsung laptops specifically
• Microsoft is investigating and working on a fix for the problem

There has been more woe for selected Windows 11 users over the last few days, with a nasty software bug locking a substantial number of people out of their main C: drive. Microsoft has acknowledged the problem, and is working on a fix.

As reported by Neowin and others, the bug triggers the message "C:\ is not accessible – Access denied". It appears to have been introduced in the February 2026 security update (KB5077181), and is predominantly affecting laptops manufactured by Samsung.

In its official support note, Microsoft suggests the problem might be related to the Samsung Share app, but that's not confirmed at this stage. What is clear is that it's crippling hard drive access and many applications for affected users.

Office apps and web browsers are among the programs that this major bug causes problems for, Microsoft reports. It says it's "presently investigating" the bug, together with Samsung, and will issue updates "when more information is available".

Files, apps, and admin tasks

Samsung Galaxy Book laptops screwd over a Windows update? from r/sysadmin

Neowin notes that only the latest Windows 11 versions 24H2 and 25H2 appear to be impacted by the bug, while according to Microsoft multiple regions are affected, including Brazil, Portugal, Korea, and India.

If you've been hit by this bug, you'll know about it: Microsoft says "accessing files, launching applications, or performing administrative tasks" can trigger the error message, and for many users it's making their systems pretty much unusable.

There is the standard safety net of an update rollback, which you can find via the Settings > Windows Update menu — Microsoft has full instructions here. Alternatively if you haven't installed the February 2026 update yet, hit pause for now.

The enterprising folk posting on Reddit have some suggestions about workarounds that involve changing ownership of the C: drive, and while this seems to have worked for some users, it's not without risks — so proceed with caution if you do try those fixes.

Follow TechRadar on Google News and add us as a preferred source to get our expert news, reviews, and opinion in your feeds. Make sure to click the Follow button!

And of course, you can also follow TechRadar on YouTube and TikTok for news, reviews, unboxings in video form, and get regular updates from us on WhatsApp too.

The best laptops for all budgets

➡️ Read our full guide to the best laptops
1. Best overall:
Apple MacBook Air 13-inch M4
2. Best budget:
Asus Chromebook CM14
3. Best Windows 11 laptop
Microsoft Surface Laptop 13-inch
4. Best gaming:
Razer Blade 16
5. Best for pros
MacBook Pro 16-inch (M4 Pro)