What do you mean by an "xpt" file? SAS can make two types of transport files. You can use the XPORT engine to make a V5 transport file (or use the new %xpt2loc and %loc2xpt macros to make V7/V8/V9 "xport" files).
Or you can use PROC CPORT to make a transportable file that can include catalogs and other SAS files in addition to datasets.
The XPORT files are version independent (unless you are really running version 6 or earlier and trying to read a dataset with long variable names or long character variables).
But the CPROT files are only forward compatible. You can read an file made with an older version of SAS than waht you are running, but you cannot read one made with a version of SAS that is newer than the version you are running.
So if you are making CPORT files with a newer version of SAS and then trying to read them with a older version of SAS you will have trouble.
But why are you doing anything with either type of export format if you are using a SAS plug in to Office?