Should I backup my computer and files at the same time?

Backing up your files and backing up your computer should be viewed as two separate tasks. This is arguably the best practice. Your computer and it's current state should be run on one automated scheduled task while your documents and files (which may be included in your original computer backup) should be backed up independently.

Why? The backup of your computer should be just that, a backup of Windows and the Software you have installed, while the second backup of all of your data (this could be many gigabytes or terra-bytes of data) should be run on a separate semi-automated schedule or even entirely manual schedule. It is good practice to have many copies of your data while retaining only one or two copies of the Operating System should be sufficient. Running your backups of data on a manual schedule allows you the protection that if a file or hard drive becomes corrupt, that the corruption is not automatically copied to your backup.

So the answer is Yes, and No. Yes, you can include your data in a system backup, but a second backup of only your data is suggested. Your data is your most valuable source while the operating system and software can always be re-installed.