There are a number of different tactics that you can try for the recovery of lost data.  This article will focus on three, starting with the most simple and leading to the most complicated.

Before going into the various tactics, let us examine how can data can be lost.  You can lose information stored on a computer for almost an infinite number of reasons, but most can be categorized into one or more of the following categories:  malware or viruses, software malfunction, hardware malfunction, external damage, or user error.  Malware or viruses refers to programs that have been placed on your computer by an external entity that may wish to do harm to your hard drive.  Software malfunctions refer to errors that occur through the use of a program.  Hardware malfunction refers to an error that occurs to the actual physical hard drive or computer (i.e. blowing a circuit).  External damage can come from a variety of sources, such as dropping the computer, spilling water on it, or seeing it damaged in a fire.  User error may refer to accidental deletion, or any number of other actions in which a user made a mistake that leads to data or information loss (possibly fitting into the other categories as well).

Tactic 1:  System Restore.  This is the simplest method and is easy to perform on most any computer that has been manufactured since 1998.  If you made a mistake (i.e. accidentally installing a virus) you can use system restore to return your computer to a previous predetermined state.  The downside on this is that you may lose some items that have been added since the restore point, but the upside is that you may be able to regain access or information that was previously lost.  This is done by going into the start menu > accessories > system tools > system restore.  It is that simple.  This is the least likely of the three tactics to get the job done, but it is also the most simple and should be tried first.

Tactic 2:  DIY Software.  Typically I recommend against this.  The recovery of data is often too complicated to try to tackle with Do It Yourself software.  These programs are typically very generic trying to take on problems that are often quite unique.  If you do choose to go this route, please make sure to do your research beforehand.  While these programs may prove successful for simpler fixes, they can often make the problem worse for more complicated issues.

Tactic 3:  Use a Data Recovery Company.  If you have deemed the problem to be more complicated, your best bet for data recovery is likely to turn to a data recovery company.    There are a number of reputable companies out there with strong track records for returning lost information in a timely and affordable manner.  Once again, do your research beforehand to make sure that find the company that best fits your needs.  Any representative who promises the world and guarantees results is one that you want to run away from - the recovery of data is never that simple.