Outlook/Exchange Contacts vanished

Just replaced a workstation for a customer who is running a small network with SBS2003 Premium and Exchange Server 2005.
The workstation is running XP Pro and Outlook 2003. All has gone according to plan except that his contacts have disappeared.
Email messages are all there but no contacts.
He also had several custom folders set up in Outlook which have also not reappeared.
I checked on the old machine for an outlook.pst file but there is only an outlook.ost file.
Any idea what's happened to his contacts?

Client was working in cached mode. I overwrote the outlook.ost file with the one from his old workstation and Viola! Contact are back.
Can't seem to get the custom folders back mind you so I guess they are stored elsewhere.

When you add Custom Folders in Outlook you either add them to the current OST or PST file or you create another one or more file.