What type of error do you get?
If the file is in use by some program you will not be able to change it.
Boot to DOS ( Not dos prompt )
Copy you current version of the file to a floppy disk. (for future needs)
Then copy the new version over it.
Reboot.

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Henri Leboeuf
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> how does one go about updating the unidrv.dll on a ms
> windows 98 system. I successfully downloaded the file in
> question but my computer prevents me from copying it to
> the system file.