FSX - Slow drive access and hang ups.

Tried running Flight simulator X. From the settings screen you can load different .cfg files which are stored under My Documents. It takes ages to open up the folder and once there, if you select a file to load there is a very long wait for it to be loaded and often the program just hangs. Using alt-tab-delete to bring up task manager and then seeing that FSX is listed as not responding; if you tell it to end the task, then task manager hangs and needs a pc reset to get anywhere. On the odd occasion FSX has actually run, if you use any of the commands such as change time, airport etc the same time lag/hang up occurs. As far as I'm aware all drivers are up to date and I've tried running it in various compatibility modes and with user account control turned off. Everything worked fine under Win 7. The only changes being the OS and I've changed from ESET to Bitdefender. I've tried running it with Bitdefender turned off and still the problem occurs. Looks like reverting to Win 7!!