outlook 2007 ost file limit

I have a user which has office 2007 pointing to exchange server 2007. He is runnig windows 7.
His mailbox size is over 20 GB, and his OST file on his latpop rached maximum size which is 19.3GB. How can I resize his ost on his laptop. I know there is a registry key I need to modify but I cannot find it.
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kosciszeAuthor Commented:
I found an article but it is pointing to
 I do not have office under Microsoft. The registry under the hkey_current_user go as far as
Rick FeeMessaging Engineer - Disaster Recovery EngineerCommented:
Create it if it does not exist:
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