I get the following error (between the stars) when booting Windows 95

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Registry Problem:
Windows encountered an error when backup up the system registry. Make sure you have enough space on the drive for c:\windows\user.dat.

This error should not cause any loss of information, but if space is not made on the drive, you may experience additional problems. Please fix the problem, and then restart your computer.

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There is over 800 megs available on the drive. Does anyone know how to fix this problem?