I use Photoshop but on one machine it freezes when I try to use Unsharp Mask or Histogram. The program works fine on my other computer. I have done disk cleanup, defrag and run loads of anti-virus and spyware. My computer runs Windows XP Pro SP3 and has 2 GB Ram 300GB hard disk Intel duo core 2.33. I tried to run System File Checker and it called for the OS disk stating missing dll files it then says can't use that as it is older than the version running. This, I presume is because the disk is XP Pro SP2. I am not sure whether the System File Checker did in fact establish there were missing files (as it didn't take long to throw up the request for the disk) or whether it was an automatic request. How do I get around this? Do I really have to uninstall SP3? Is there an easier way? I should add that the Photoshop program used to work fine on this machine but then suddenly had this problem. Unfortunately I haven't been able to use System Restore as it was conflicting with my (then) firewall Zone Alarm.