Fix Windows MBR

Using MbrFix is the simplest way to fix it.
Download MbrFix then open console.
(Start->Execute->cmd)
Change folder to MbrFix folder.

MbrFix /drive 0 fixmbr

If this method is not working, please check the following reference.

cnet download - MbrFix
CoffeeCat's IT Blog - 在Windows下删除Linux系统的方法（附修复MBR的工具下载）
Age of Engineer - 在Windows XP SP2下修復MBR
daqi's blog - 卸载ubuntu的正确方法