I seem to be having trouble with the zip's too. I keep getting a message that a file is corrupted, and I should don-load it again. I delete all the files, download them again, and get the same message. Something about it might be a multiple disk zip? Any suggestions?
Maybe it will help to get the latest version of WinZIP (www.winzip.com). I often use WinRAR (www.rarlab.com) to extract ZIP files, you could try that too.