the more changes you make, the less likely it is that windows will be able to adapt. the reason is that during install, it loads only the drivers necessary to run your current setup. it needs different drivers (from the cd) to run certain things. you can try a repair, but it's usually going to format everything anyway.
the best way to import your old stuff is to either:
a) save a copy and then copy it over using a floppy, flash drive, CD, dvd, or other removable hardware after you've reformatted the hd.
b) if you are installing a new hd, attach the old hd temporarily and copy the data files over (don't copy over windows. there will be a .dll conflict if you have two different versions in the same path.)
c) use the import files and settings wizard (or whatever it's called.) i usually do a), but windows can automatically import your old data to your new computer.
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