Go to the Routine used to depreciate one asset, select the asset to undo depreciation for and set a new depreciation date. Example: If an asset was depreciated through February and you need it back in January, simply set depreciation to run through January. GP will warn that the depreciation is being backed out. A reverse GL transaction is created with the GL Posting routine.
This is not available for a full depreciation run but it works great for a single asset. A Word macro could be used to back out depreciation for multiple assets.