An explanation of terms used on this page can be found here.
When a file is deleted it is not immediately destroyed; the space that the file
occupies is marked as free space (to be used again for other files) but the
contents of the deleted file are still on the disk. Therefore it is possible to
undelete a file, but speed is of the essence: the operating system may re-use
the space that is occupied by the deleted file and when that happens, the data
if you need to undelete files from a drive that is normally submitted to heavy
use (like a system volume), you may want to consider purchasing the license
immediately and skipping the use of the trial version (or any 3rd party trial
versions, for that matter). Not wasting time and only installing software that
actually helps the situation will increase your chances of success
dramatically. Remember, if the program doesn't help you we
will refund, though it will obviously never hurt to have an undeleter ready
for use at any time.
Please note: if other additional problems exist (such as
hardware problems, volume corruption, or read errors) you should use iRecover.