if they are seeing the Kernel32.dll it's a pretty safe bet to assume they are using 98 or ME since XP runs on the NT kernel ;)

doing a reinstall or reformatting would be my last line of defense. But sometimes corrupt files just happen, and happen often with a win98 system. It's not nearly as stable as the 2000 or XP systems running on the NT kernel.

Try a bit of troubleshooting .... never can tell .... could be something as simple as replacing a file.

If all else fails reformat. Even Microsoft recommends you reformat a win98 system once a year. Not that I would now ... but they do recommend it