Hi.
The best solution is
- to install the linux bootloader not into your MBR but into the boot record of the linux root partition
- to copy your LINUX boot sector into a file
- copy that file on your windows partition
- refer to that LINUX-bootsector within windows bootloader-ini-file "boot.ini"
There's a wiki-page about that:
http://wiki.linuxquestions.org/wiki/Dual_booting
good luck,
Stephan
P.S.: You don't have to reinstall Linux for that.
If you don't have a boot floppy disk for your Linux,
take a Knoppix or just another Live-Linux CD in order to
get access to the commands mentioned in the WiKi