Excel slow to browse folder during open

After upgrading from Office 2000 to Office XP (2002) Excel takes up to 1 minute to show the spreadsheets in a folder when using the
File->Open dialog box.

The folder in question contains 9,400 spreadsheets averaging around 40 KB each, but was never slow to display with excel 97 or 2000.

I have installed Office XP SP3 and all patches available from Office Update.

Any suggestions would be welcomed.