Classes.dat, used only on Windows ME, contains the CLSID Key previously stored on the earlier versions of Windows in the System.dat file. This new file was added in order to allow the Registry to be greater than 11 megs. In Windows 98, Windows may report the inability to load a Registry that is greater than 11 megs, in Windows 95 the limit is 8 megs.

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thanks for the short info, lleoliveira.

My Win98 & WinME systems have never reached those registry limits. In fact, the bigger the registry files get, the greater the chance you will have registry problems. these registry problems can make Windows 9xME systems less stable.

if you are near the limit I would suggest running Registry Checker (DOS) version with the /opt switch. Type scanreg /opt at the DOS prompt outside of Windows to compress the registry files. Small registry files mean better performance and less problems with the registry.