While there is no direct way to undo a depreciation run, here are a few suggestions on getting back to the prior calculations.

In Sage Fixed Assets - Depreciation:

• Run Depreciation to the correct date. The program is designed to run depreciation to any given date into the past as well as the future. If depreciation is normally calculated monthly, and it is accidentally ran for a date other than the month after the Current Thru date in the asset can be corrected with two depreciation runs. First, run depreciation for the period prior to the desired period, and then for the desired period. See Depreciation this run is too high for more information
• For example: If depreciation was ran through 12/2012, and it is accidentally ran for 06/2013. To get to 01/2013 depreciation numbers, run depreciation back to 12/2012 and then to 01/2013.
  Or:
• If there is a recent backup of the database: Restore from backup. This method may be a drastic step, depending on how many other changes have been made since the last time a back up was made.