Here are some items to check if your serial number is not accepted:

1. The first thing to check is to make sure you downloaded the correct version of the program. Check the order to make sure that it lists KForce PC Edition version and not Pocket PC edition. Also make sure that the build number matches between what is installed and what is on the serial number.

2. Your name, as well as the serial number, must match exactly what's shown on your email receipt. Do not use any abbreviations.

3. Make sure there is not an extra space anywhere. There should be just one space between the first and last name. Do not enter in dashes.

4. If that doesn't help, uninstall the software through the Windows Control Panel and reinstall the software again.

5. Close KForce and run the support file below then open KForce and try your serial number again.
http://www.allprosoftware.com/technicalsupport/SupportFiles/delkforcecfg.bat