By default, Outlook places each Offline Folders (.ost) file and Personal Folders (.pst) file that it creates in the %userprofile%\Local Settings\Application Data\Microsoft\Outlook folder. This setting will allows you to change the default location and store the files in different location in different folder.
1) Shutdown outlook > Copy the OST elsewhere > Control panel > mail applet (use the search box and search for mail if you can't find it) > select your profile > properties > email accounts
2) Select your Exchange account > Change > More settings > Advanced > disable cached mode (uncheck the box) and click Apply
3) Press the Outlook data file settings button > Disable offline use > OK > re-check cached mode
4) Outlook data file settings again > browse > point to new OST location > OK out of the dialogs
Method 2 :
Open your registry and find the appropriate key below.
Create a new REG_EXPAND_SZ (Expandable String Value) value called 'ForcePSTPath' and set it to the path of the required personal folder directory (e.g. "C:\Mailbox").