Lotus 1-2-3 is a spreadsheet program that is now manufactured by the IBM corporation. Lotus was the first major spreadsheet program and set the standard for many of the spreadsheet programs of today, such as Microsoft Excel. The file extension that Lotus uses is "wk4." Since this file type is proprietary to the Lotus software, you will be unable to open it in MS Excel to save it as an "XLS" format without changing your registry
Point your internet browser to "Support.Microsoft.com/kb/938810/." Scroll to the middle of the page to find a link that downloads a file to enable blocked Excel file types (the .wk4 type is one of them). Click on the link to save the file.
Choose where to save the file. Browse through your computer folder until you find the file save location. Click the "Save" button.
Locate the file on your computer. Double-click the file to begin the installation. This file will change some of the computer's registry values.
Open Excel. Click on the "File" menu and select "Open." Click on the pull-down menu next to "File Type." You should see ".wk4" as an option. Browse through your computer to find the "wk4" file, click to select it and click "Open."
Click on the "File" menu once the file has opened. Click on "Save As." Click on the pull-down menu, choose "Xls" from your file options and click the "Save" button. The file is now saved with the "Xls" format.
When you save the file as an XLS, the original wk4 file will not be deleted off your computer. If you no longer need it, be sure to delete it to free up memory space.