Does anyone have any information about whether Fortran 90 in general, and Microsoft Fortran Powerstation 4.0 in particular, has any compatibility issue with Windows XP?

If yes, any knowledge about possible remedies?

You can use your compiler on Windows 2000/XP but be aware that MS no longer supports Fortran Powerstation and the last version I had from Dec (the company that bought it from MS) caused all kinds of problems if loaded on the same machine with the MS Visual C++. The two just don't live together. So load them on separate machines or don't say you were not warned.