Download a reputable antivirus scanner (Malwarebytes, Kaspersky, or Windows Defender). Run a full system scan. This will quarantine and remove the malware executable, preventing it from encrypting any new files you recover.

While "happ decrypt" tools are useful for developers, users should exercise caution:

If your files have been renamed from document.docx to document.docx.happ , your system has been compromised by a ransomware strain that identifies itself by this extension. This extension acts as a "lock," signaling to the operating system that the file format is unreadable without the specific decryption key.