This doesn't make too much sense. After the upgrade, using the VERY SAME configuration of the previous version, Windows XP Pro seems not able to read or to "understand" the files correctly. Well, more in detail. I run Outlook 2007 using a PST which resides on a network directory (let's say X:\mail, which seats on my mac drive), this file is a 600Mb file (so not so big). After the update, Outlook is not able to recognize anymore the PST file, saying that is not a Personal File Type. I tried this other way. I copied the file to the local disk and I added the data file to Outlook manually, and it works ok. It seems that somehow, while reading big files from the shared directories, something get lost. The file is ok, but can't be read properly. The copy of the file works ok. Even if I redo the network drive mapping, same results. This problem doesn't occurs while opening and working with smaller size files. This is a HUGE problem. Please, help!