This field should not be null (Remove me when you edit this field).
There are two ways to do this:
A. If you haven’t checked in any files since you started modifying them then the process is simple:

B. If you aren’t so lucky and have made some commits along the way then the only option is to use the Rollback command:
To use this you will need to install Team Foundation Server Power Tools v1.2
Figure: The last revision before Tristan made changes was 5367

It would be nice if there was a GUI for this tool so that I can just right click and select rollback.