ToDoList has an excellent mechanism to make updating the software very easy.

ToDoList is very good about not corrupting data between releases. However, precautions should always be taken in case the unexpected occurs. Before an update get a backup of all of your .tdl ToDoList data files, all .ini files, modified .xsl files, .csv time logs, and any other related data. To backup the software itself, just drag/drop a copy of the ToDoList folder. If your configs and other data are stored elsewhere then you'll need to do that separately.

To check for updates automatically. See the checkbox: menu > Preferences > General > Automatically check for updates on startup

To check for an update manually for your current release, go to: menu > Help > Check for Updates…

ToDoList makes a network connection to the update server. When checking manually, a short message confirms if an update is not available.

Release notes are displayed so that you can decide if you'd like to upgrade. The window asks “Would you like to update to this version?”. Clicking the Yes button causes the following:

• The program TDLUpdate.exe is executed.
  • You will probably need to confirm execution of this from a User Access Control (UAC) prompt.
• ToDoList closes.
• The new release is installed to a temporary location.
• The new release is copied over the existing version.
• ToDoList is restarted.
• The same .ini that you were originally using is reloaded.
• All tasklists are reloaded.
• A notification message will appear confirming the successful update.

At this point you are running the new release with almost no effort at all.

You can check your current release from Help > About ToDoList. Release notes for all recent releases is available at CodeProject.

Downgrades are virtually unheard-of. The software is tested extensively in a cycle that includes multiple beta versions, a few release candidate versions, and then the final production release. However, as this software is community supported and the release is only as good as the reports of people who are testing the pre-production releases, it's possible that required functionality may be broken after an update. Dan is very good about posting updates to address critical issues. But if you do need to downgrade fast, all previous releases can be found here.

Please note that as with most software, once your configuration files and .tdl files have been upgraded, they may not work the same with a prior release. They really should, as there are few “breaking changes” ever introduced in this software. But before a last-resort downgrade you should check in the forum to find out if there are any expected issues.