Short answer... you cant unless you boot from a linux live cd and rewrite MBR and add an entry for booting windows and one for linux.
That is because you did not have 2 drives: one for each OS.
Each OS could use one partition on same drive, but since the drive has only one MBR both OS rewrite it in order to ensure its proper boot secvence...
Windows boot manager can`t properly start linux... so your only choice are to use linux boot manager to start it and windows...
Google it... there are plenty of tutorials out there: http://lifehacker.com/5403100/dual+boot-windows-7-and-ubuntu-in-perfect-harmony