Fc2-ppv-1261799-1.part6.rar -

Use updated versions of WinRAR or 7-Zip. Older versions of extraction software may throw "Header Corrupt" errors if they don't recognize newer compression algorithms.

Given the presence of "PPV" in the file name, it's likely that this file is related to a video or a live event that is available for purchase on a pay-per-view basis. FC2 might be a platform or service that offers such content. The .part6 designation implies that this file is one of multiple parts of a larger file or collection. FC2-PPV-1261799-1.part6.rar

Always run an antivirus scan on the final extracted file before opening it. Use updated versions of WinRAR or 7-Zip

This usually means one of the parts (possibly part 6 itself) was interrupted during download. You may need to redownload that specific part. FC2 might be a platform or service that offers such content