Hi
Ewandude
I assume you mean encrypted with EFS (Windows' onboard Encrypting File System), well it's the same on Windows 7 so there should be no problems using them on 7. BUT do remember to back up your encryption certificate before you do the install, this is the procedure they recommend from Microsoft:
Also remember to backup the files
Regarding the zip files, just make a backup, and install winzip (or better yet winrar) on Windows 7 and you're good to go.
As you might deduce I would recommend you do a backup of your personal files and then do a clean install , never-ever do an upgrade it's just asking for trouble.
You can easily use your upgrade disk to do a clean install.
There's a good guide on Paul Thurrorts Winsupersite for just that.
Regards
RabidSquirrel