Hi,
Click Start, type regedit.exe and press Enter.
Navigate to the following branch:
HKEY_CURRENT_USER\Software\Microsoft\Windows\Curre ntVersion\Explorer\FileExts.zip
Delete the sub-key named "UserChoice"
Close Regedit.exe
If that does not help, get the .zip file association fix from here:
File association fixes for Windows Vista:
http://www.winhelponline.com/articles/105/1/
if its not helping try third party software like winzip or winrar which can handle almost all zipped formats