If I were you, I'd copy the bootloader's (grub/lilo/something) configuration before reinstalling Windows. That way, after the Windows has been reinstalled, you've wiped out your Linux bootloader, reinstalled Linux bootloader and are possibly wondering why something is missing from it (Windows not autodetected, can't remember how it was configured there..) you can simply replace the automatically created config file with the one you had working before. If the partitioning has not changed (i.e. Windows is still using the same partitions as it used to, and so is Linux), then you should be fine just replacing the config, avoiding doing anything "by hand".
EDIT: Matir, I wish I had heard that some years ago on the other hand, failing is the ultimate way of understanding and learning..