hi
Close outlook
a) First try this.
Press CTRL+SHFT+ESC
Go to Process Tabs
Open task manager - see if there is any outlook process.
Right Click on outlook and kill it.
try to open outlook again and see if that works.
b) Otherwise do this.
Download this free tool. unlocker
http://download.cnet.com/Unlocker/3000-2248_4-10493998.htmlNavigate to where your outlook file is (OST) - right click and select unlocker.
Select unlock
If any application is locking the file - those locks will be removed so that you can start outlook.
After removing locks try opening the file again.
hope this helps.