The operating system upgrade didn't give me any problems.
The upgrade to XL 2002 was a problem only when I compiled on 2002, took it to work, and tried to run the compiled code on XL 97. "Unknown Error" was popular.
XL 2002 VBA is not exactly backward compatible. If you code exactly what XL97 needs, you won't have problems. But if you think that XL 2002 is exactly XL97, that's a mistake.