Sure, that can be done. If you just need to backup some important files, its easier, but you could also copy everything over if you wanted.
Make sure you have partitioned hda, make a new folder, open a file browser in X, copy each folder off / to the new folder on hda with the exception of where hda is mounted (since could cause an ugly recursive problem). You may run into problems if you try to copy everything back over after you reinstall your distro.
The best thing (I would think) to do here would be to just back up the files you can't get again. If you are reinstalling, why not do a clean install, then after thats done, connect to the internet or whatever and get the programs you want? That seems like it would work best to me. But then again, this just may be my Windows-brain kicking in telling me to do a clean install since thats the only thing that helps that beast of an OS sometimes