This is a multipart series on backing up your computer (at home or the office). 

Part 1 - Decide what needs to be backed up.

First you need to figure out what actually needs to be backed up.  This may be an easy step if everything you work on goes in your "My Documents" folder.  However, if you have stuff scattered across your hardrive it may be a bit more of a chore.  Many programs store your files in default locations.  Let's look at each type of application and see where the files we need to back up are located.

Email
Email is probably one of the most important applications.  Some people (for better or worse) store everything in their email box.  I use Outlook at home and the office.  At the office your information is probably backed up by your server administrator so you shouldn't have to worry.  You may want to double check just in case.  Let's concentrate on the none corporate environment, i.e. home, home office and small office.  You either have a dedicated email client like Outlook, Outlook Express, Thunderbird, etc or you use a hosted service like Hotmail, Yahoo Mail, Google Mail, etc.  If you use the hosted service this should be fairly safe.  Let's focus on the email clients. 

Email Clients
So you use Outlook or another email reader.  These typically download messages from the email server to your local desktop and store them in a file.  In the case of Outlook these are stored in a file ending with a .pst extension.  You can find this file by clicking the file menu then Data File Management.  The dialog box that comes up will display the path to your Outlook data file.  You may have more then one.

You can either leave the file where it is or move it to a more convenient spot.  I will talk about this in Part 2.  So now that we have found our data file we need to make a note of the location and include it in our backup plans. 

Your Documents
A large number of people store their documents in the "My Documents" folder simply because it is the default save folder in many applications.  If all your documents are here then you are in luck.  Otherwise you need to find all of your documents and either organize them or keep track of them.  More about this in Part 2.

Personal Finance Files
Do you use Microsoft Money or Quicken?  If so you have a file that contains all of your financial information lurking on your computer somewhere.  You need to find this.  In Microsoft Money you can click the File menu and then Backup and this should open up in the default backup folder.  Money is smart enough to make a backup of of it's data file.  So you should see a file with the extensions .mny and some files with the extension .mbf.  Make a note of this location as you need to back these up.  You can also change this location.  More about this in Part 2.

Media
Here's where it gets messy.  Media files are photographs, movies, audio files, etc.  In other words these are your vacation photos, your wedding videos and your Itunes music files.  So these files are one of a kind so they should be backed up.  The problem?  They are usually gi-normous (really big).  You need to find all of your media files and these can be difficult to track down because your camera stores photos in one directory, your video software in another and your mp3 collection is in another location.  You need to find all of these files and note the location (more on this in Part 2).