Orange have upgraded me from an 8100 to 8120, I've followed the instructions in the desk top software and sync it, however every entry on the BB is duplicated, but not on the Outlook.

Any ideas how to clear all the duplicates on the BB

If you have exactly the information in Outlook you want on your Berry, you can do this.

1. Go into mail, phone, calendar, task, and memo pad options and disable wireless sync.
2. Use the Desktop Manager to do a Backup of your Berry data
3. Under Backup and Restore click the "Advanced" button.
4. In the right column, one at a time click on the entry were data is duplicated
(address book, calendar, etc.) Next click the "Clear" button. Repeat until
you have removed all of the offending duplicate entries.
5. Go back now and enable wireless sync everywhere you disabled it.
6. Do a battery pull for about thirty seconds, and put it back in.

When your device comes back up, it will resync with Outlook, and you should have only one entry for all of your data.

I have the same problem. Did what you suggested however when you sync again, even with replace target data checked, it still creates duplicates, triplicates, etc. until I clear it again. Is this an issue with the 4.3X RIM OS? Us luckly (in this case unlucky) users got 4.3 with the 8120