On an HP system with vista, user can no longer open certain files. Main example is word files arriving as email attachments. Word file was scanned by the AV and found to be clean. File can be saved on the PC but not opened. The file when forwarded to an xp sp3 user was scanned clean by Nod32 and could be opened and read. What's happening with this Vista system? It could read doc filles and now it can't? Advice please.