a) Completely un-install SONAR from your computer. This is normally done from Start menu / Programs / Cakewalk / Sonar / Uninstall. Choose "yes" if the routine asks you to remove any shared components. This will not remove any of your files or audio data.

b) Make sure nothing else is running while reinstalling SONAR in step 'e'. In Win 98/ME/XP, choose Start | Run and type MSCONFIG. Click OK, then click on the Startup tab at the upper right of the window that opens. Uncheck all items listed, click OK, then restart your computer.
You can always recheck those items again at a later time. In Win 2000, click Ctrl+Alt+Del and manually End Task on the items you don't need running.

c) Click the Windows Start button and select Run. At the prompt type REGEDIT and click OK.
Backup your Registry before making edits - you do this by clicking the Registry menu, Export Registry File.
Now delete the following Registry keys
HKEY_CURRENT_USER\Software\Cakewalk Music Software
HKEY_LOCAL_MACHINE\Software\Cakewalk Music Software

Please note that this will remove any effects presets and key bindings you may have made in Cakewalk. You can back up those registry keys separately if you like.

d) Delete the files AUD.INI and TTSSEQ.INI from the SONAR program folder, located in C:\Program Files\Cakewalk.

e) Restart your computer, then reinstall SONAR and the patches from www.cakewalk.com