Backupnik is a very simple backup application. So simple that I spent more time removing options and simplyfing things rather than actually implementing features. Backupnik is freeware and won't cost you a penny, regardless of where and how you use it.

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Disclaimer: I won't take any responsibility for data loss, damages to your computer or any other disaster that may result from the use of Backupnik. Seriously, test it for yourself with bogus files and folders before putting your life in its hands.
Please read the mini-guide below before using Backupnik.
If I haven't scared you away, you can download the latest version (1.0.2) (about 0.5 MB).

Requirements

Backupnik works on any Windows starting from XP.
It requires .NET 3.5 SP1: if the application doesn't start you are probably missing it. You can download it for free from Microsoft's website.
If you are running Windows XP you also need the W2003 Resource Kit (11MB, free). Newer versions of Windows already include the robocopy utility and shouldn't need this.

Mini Guide

There isn't much to say: Backupnik copies the folders you choose into the destination folder (for ex. an USB key).
The important thing to understand is that Backupnik uses the Robocopy utility with the /MIR option. This means that files that have been deleted in the source directory since the last backup will be deleted in the destination folder as well.
In other words, Backupnik won't keep an history of your files, but will simply mirror the current contents of your directories.

Questions and Answers

The application doesn't start.
You are probably missing the latest .NET framework. See requirements above.

I get an error "Cannot start robocopy"
You are probably missing the robocopy utility. See requirements above.
If robocopy is installed, please make sure that the PATH environment variable contains the directory where robocopy.exe resides.

Backup fails for some folders and the only message is "Backup failed".
You probably have insufficient privileges on the folder. Robocopy needs Auditing permissions on the source directory.
Starting Backupnik as Administrator should be enough (right click on the application icon/"run as Administrator").

Where are the advanced options?
There are no advanced options. Backupnik was designed to be simple, if you need more control you better look into a different application.

What is the actual robocopy command you are using?
robocopy "source_folder" "destination_folder\name_of_the_source_folder" /MIR /XJ /NFL /NDL /R:1 /W:1 /COPY:DT /LOG+:"%tempdir%\Backupnik_Log.txt"

I think I've found a bug.
Great! Please write any bug report, comment or suggestion to backupnik@frenk.com. Positive comments are also welcome, if you like this software please let me know it!
If this software is being useful to you, please consider a small donation.