How, when and under what circumstances does it say "file invalid"?  Did you reinstall Peachtree?  Copying the files themselves is not sufficient.

Software Sales, Training, Implementation and Support for Exact Macola, eSynergy, and Crystal Reports
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First of all, if you "copied" the data (folder and or files) to the new machine, then a restore will not be possible as only backup files can be restored.  If however you copied backup files and are unable to restore this is a horse of a different color.

Has the drive on the old machine completly failed? If not, I suggest trying to restore to a new location on that drive first to see if the backup files are good.  If they are not, try another backup.  If it still fails to restore to the new system try to copy the data files only to the new system and try opening the company again.  Be sure you are running the exact version and updates before trying this!

yes i copied backup files from bad disc,via burnt cd

 so your saying this should restore?

disc is very unstable,about to fail

If the backup files are good you will be able to restore them to the new pc as long as it is running the exact version(including updates).  If verify the same version including updates and still get the same error when trying to do a restore then the backup file must be corrupt.  If you are still able to access peachtree in the old pc, you can try doing another backup.  Otherwise you may have to try copying the raw data from the old pc to the new (not recommended unless you have no other options.