Are .CHK Files Safe to Delete?

The verdict

Safe to delete once you have confirmed your real files are intact. A .chk file appears when Windows runs CHKDSK and finds data it could not reattach to a file. It saves those loose clusters as FILE0000.CHK, FILE0001.CHK and so on inside a hidden FOUND.000 folder at the root of the drive. They are recovery leftovers, not something Windows uses.

When to keep them

Keep the FOUND.000 folder only if you are actually missing files after a crash, bad shutdown, or failing disk. In that case a .chk fragment may hold part of a lost document. If nothing is missing and the PC runs normally, they are dead weight — a drive can accumulate hundreds of megabytes of them.

How to recover something first (optional)

1. A .chk file has lost its name and extension. If you need the data, try opening it in a text editor (for documents) or rename it with a likely extension (.jpg, .docx) and test.
2. Tools exist that batch-identify CHK contents by file signature, but for most people there is nothing worth recovering.

How to delete them safely

1. Delete the whole FOUND.000 folder. It is hidden and system-protected; enable "Show hidden files" and "Hide protected operating system files" off, then delete it, or remove it from an elevated Command Prompt with rd /s /q C:\FOUND.000.
2. Disk Cleanup will also clear them under the drive scan.

Is a .chk file a virus?

No — a .chk is inert recovered data, not executable code. It cannot run on its own. Deleting it is always safe for your system; the only risk is throwing away a fragment of a file you still wanted.