If you accidentally delete some files, you can try to use some file recovery program to recover these files.
One of the most famous file recovery tools is r-studio or r-undelete, which can you can download a trial version here(http://www.r-studio.com/ ). However, it's quite expensive.
A free tool available is Recuva (http://www.piriform.com/recuva). this is quite promising as it is produced by the company that create the CCleaner. I have recovered some file successfully with this tool.
A Tip: If you accidently delete a file, you should stop writing any file into that hard disk to prevent damage to your deleted file.