hi,

To fix this problem, do the following:
1: find 7-zip file manager in your start menu
2: context menu the file manager and hit enter on run as administrator, accepting the uac dialog by hitting alt y when it shows up
3: in the 7-zip manager window, hit alt t for tools and hit enter on options
4: in the system tab, if you want to associate 7-zip with all supported file types, go to the list of file extensions and hit control a and hit enter on both unlabeled buttons next to the list. To make sure that all file types are associated, make sure that the list shows 7-zip on both the columns for system and your username. Once you're done, hit enter on apply and ok, then either close explorer and re-open it, or log off and back on, or reboot. This will also add the crc-sha option in your explorer context menu to verify checksums, hth