I have WinXP so I am less familiar with Win 7. However, with many Windows O.S.'s sometimes it's necessary to do what is called a "clean" uninstall.
This involves opening regedit and in two areas: HKEY_CURRENT_USER\Software and HKEY_LOCAL_MACHINE\Software.
Within the "Software" folder of both those locations should be a subfolder named Cakewalk Music Software, or simply Cakewalk. You want to highlight that main Cakewalk folder and delete it. Editting your Registry like this would be step two BTW.
So the actual steps would be to first uninstall Cakewalk as you normally would do, then edit the registry as described above, then go into C:\ Program Files\ and delete the CWAF and Cakewalk folders that might be left behind.
Uninstalling Cakewalk might actually remove all of these items but it's important to make sure and delete them if they are still there.
Then you can restart the PC and install Cakewalk as a fresh install. Hopefully this helps. Also make sure you have any firewalls and Anti-Virus applications disabled when you uninstall and install.