If you have set options in "System settings" page, you can start MultiPar by selecting a recovery file. This way is easier than opening a recovery file by pushing "Open" button after you start MultiPar. Even when there are multiple recovery files of same set, you must select one of them. If you happen to select multiple recovery files, Create window may open, or multiple Verify windows will open.
  While you may verify written files on read-only media like CD-R or DVD-R, you cannot repair damaged files immediately. When you repair files, you need to copy those files on HDD. Even if they are damaged files or fragments of unknown filename, you should bring all source files and recovery files to a folder on HDD. To retrieve as many data as you can from the damaged media, you would better use "File Salvager software". There are many shareware and freeware for the purpose. Because "Data Recovery service" by a specialist company requires more money, it's the last way to restore important data.
  When some vital packets are missing in a PAR2 file, it will be hard to verify or repair. But all kinds of packets may exist in multiple PAR2 files. Because MultiPar will search other PAR2 files of same base filename in the folder automatically, you should set same base filename for all PAR2 files of the same recovery set. (Base filename is a filename except extension and volume number.) When other PAR2 files are put in another folder, or are renamed to different base filename, you must add them manually by "Add" button.
  Get more blocks as possible as you can. If there is a same source file on different location, you should copy it or add it by "Add" button. You need to find more blocks from the damaged media. If you cannot recognize fragments are pieces of which source file, you select "Additional verification" at "Verification level". If there are old files of modified version in a previous backup, it is worth to add them.
  When a transported file had been damaged already, you cannot salvage lost data on your side. If there are other recovery files, you get them, too. If there is same file on another site, you may get it again. Or, you may ask someone to give another set of recovery files.
  Mostly this is caused by "exclusive file access" or "limited privilege". While a damaged file or recovered file is being accessed exclusively, it's impossible to replace them. An example is Anti-Virus scanner, and you may need to exclude working folder from real-time scan. When status of a damaged file became "Locked" after failed repair, the file is being used by another application. Of course, you cannot repair (modify) a system file, which is protected by OS. When repair was failed by a fault of PAR1/2 specifications, you may solve the problem by getting one more available block.