You did not say in your post if your partition is NTFS or FAT. If it's FAT you should be able to write to it safely. If NTFS, I would not. In either case, you should have all important files backed upfirst, to cd/dvd/etc. If you're not sure, under Windows, you can click on 'My Computer', then right-click on C:. The resulting dialog box will show what tpye it is.