Extraction errors: CRC errors, missing parts and “unexpected end of archive”

You right click part 1, hit extract, and WinRAR or 7-Zip throws up a box of red errors. Deep breath. In almost every case the build itself is fine: one piece of your copy is damaged or missing, and you can usually fix it by replacing just that piece.

First: read which file it names

Error windows usually list the exact file with the problem, such as MyBuild.part17.rar. Write that down. It tells you which part to fix, so you do not need to download the whole build again.

“CRC failed” or “checksum error”

What it means: a CRC is a fingerprint stored inside the archive. When the extracted data does not match its fingerprint, the program knows that part got damaged on the way to you.

How to fix it:

1. Re-download the part named in the error. Delete the old one first and keep the same file name.
2. If you used Usenet, run a PAR2 repair instead. PAR2 files are recovery files posted with the build that can rebuild damaged pieces. NZB Grab, SABnzbd and NZBGet do this automatically, so check the client’s history: if it said “repair failed”, see my download failed.
3. If the build came with an .sfv file, open it with a checker such as QuickSFV. It tests every part and tells you exactly which are bad.
4. Extract again.

“Unexpected end of archive”

What it means: a part is shorter than it should be. The download stopped early, or the file was still being written when you tried to extract it.

How to fix it:

• Make sure every download has really finished (no browser downloads still running, no torrent still at 99%).
• Compare the file sizes. Parts are normally all the same size except the last one. A part noticeably smaller than its neighbours is your culprit. Re-download it.

“You need to have the following volume to continue extraction”

What it means: a part is missing, or it is not where the program expects it.

• Check every part is in the same folder.
• Check the numbering runs without a gap (part01 to the last part).
• Check the names have not been changed. Browsers sometimes add (1) to a file name if you download it twice. Rename it back to match the others exactly.
• Download the missing part.

“Cannot open file as archive” or “unknown format”

• You may be opening the wrong file. Always extract from the first part.
• The file may not have downloaded properly at all. A “RAR” that is only a few KB is probably an error page that saved by mistake.
• Your tool may be too old. Update WinRAR or 7-Zip to the latest version. If 7-Zip struggles with a RAR build, try WinRAR.

Wrong password, or it asks for one

Most builds have no password. If yours asks for one, the build’s post will say what it is: check the post carefully. Copy it exactly, with no extra spaces. A “wrong password” message can also appear when a part is corrupt, so if the password is definitely right, treat it as a CRC error and re-download the named part.

It stops part way with a disk error

• Not enough space: you need room for the parts and the extracted build at the same time. Free some space or extract to a bigger drive.
• “File too large” or it stops at 4GB: the destination drive is formatted as FAT32, which cannot hold files over 4GB. Extract to an NTFS or exFAT drive instead.
• Path too long: extract to a short folder near the top of a drive, such as D:\Builds, rather than deep inside other folders.

Your antivirus deleted something

If extraction finishes but files are missing, or it fails on the same file every time, your antivirus may have quarantined it. This is very common with emulators. Read antivirus false positives before you do anything else.

Last resort

WinRAR’s extract window has a Keep broken files option. It lets the extraction finish even with errors. Use it only to see how far you get: a build with damaged files may not boot, or games may crash. Replacing the bad part is always the proper fix.

If one download method keeps giving you bad parts, try another option in the download box. Usenet with PAR2 repair is the most reliable; Newshosting’s Arcade Punks deal is 70% off plus 3 free months.

Still stuck? Leave a comment on the build’s post with the exact error and part number, or ask in our Discord.