How to get to know how to change the drive letter in Windows 2000 guide:
Click Start, Help, in the Windows 2000 Help select Index tab, in the "Type in the keyword to find:" box type in the "drive letters", find "changing", double click on it, read the manual, and if you still want to reformat, you have the full power to do that
And why would you want to change the system volume drive letter? (just curious)
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