The archive is either in unknown format or damaged?

Answer 1

If you're talking about WinRaR file format .rar then there are 3 main reasons why you get this error

1) The file you have is not .rar file.It could be some junk file which ends like .rar(but in reality it is not).

E.G.

I can take a movie .avi file and instead of .avi type .rar...of course that file won't work

so..If you downloaded that file from somebody,it could be junk

2) If you used FireFox to download the file,do not "play" too much while file is downloading.try to avoid "pause" and "resume" options.Just leave it to download without interruptions. rar file is very sensitive because it is highly encrypted.If something VERY VERY little goes wrong during download,the WHOLE file becomes useless.

3)person who UPLOADED the .rar file made the mistake described on #2

....

For more advances users.Here is how to find out if the file is really .rar or it's junk.

...

take the corrupt .rar file and add .txt extention in the end.Do not delete anything.

E.g. if your rar name was this_istesting123.rar now it'll look like this_istesting123.rar.txt

Double click to open the file.Notepad will show up because it's text file.

NOTE: if your file is large,like 100MB PLEASE BE PATIENT because it may take up to 5 MINUTES to open that huge encrypted notepad.

Once you have it open look at the first line.if you see something like this

" Rar! ϐs " then your file is real .rar file and it is NOT junk.Probably your connection was interrupted during download and file just got corrupt.Re-downloading the file will fix the problem.Please don't forget about #2 problem.

Hope this helps.Bye.