The prel file is your Premiere Elements project file. It is created when you first start a new project and is updated every time you make a change to the project and save it. When you first create a project, you specify a name and a folder location where it will be stored. You will need to know this folder location to edit the file.
I'm assuming you're using Windows. There are a number of ways in which to open the file in wordpad, but each version of Windows is slightly different. Which version are you using? XP? Vista? Windows 7?
You can open wordpad from the Start button. Click Start, All Programs, Accessories, and then click WordPad. Once Wordpad has started, bring up the Open files dialog. The keyboard shortcut is ctrl+O (that's the letter O, not zero). The Open dialog will have a navigation window like Windows Explorer does. Go to the folder where you created your project. You probably won't see anything listed in the box because the default is to show only Wordpad documents. There is a dropdown selection list next to the filename field where you can change that to "All Documents (*.*)", change that and you should be able to see your project file. Select the project file and click the Open button.
Note: the default is to not show the file suffix, if that is how your system is set up, you will need to look at the icon next to the file name to determine which is the project folder if you have more than one file with the same name (there is a log file that will have a "page" icon, the prel will have a "pre" icon). Alternately, type the project name in the file name field. The full file name with suffix should be listed -- select the prel file.
Once opened, use the find command to locate the WorkBarAdjusted text. Then change the text that follows from True to False and Save the file.
Before you edit the file, I'd strongly recommend making a copy of the file so you can restore it should something go wrong. You don't want to lose all your work.