Access Sorting in Access 2000

[rrs18]

I have an application written in Access 2000 (by me) that no longer recognizes the prefix sorting instructions in a report. For example, in a design view, under sorting, i can no longer use the prefix characters parameter. When i do i get the following message:
Function is not available in expressions in query expressions 'Left(Lname, 2)'

This used to work, but this is the first time using Vista. Has something been discontinued?

Thanks