Yep agree messing with the Mbr and possible to hose the windows 7 boot menu. Makes for a more troublesome fixing,adding,changing default boot order. And requiring repairing always a hassle.
Had a Win 7,Win XP dual boot. And decided to install Mint so during the install choose the something else to allow me to configure the partitions myself. And in my case root / was Sda4 but the default setting at bottom was set to Sda0 for boot loader install. So change it to point to my Sda4 "/" root partition. Then download easyBCD for my windows 7 side and ran it to add the mint bootloader to the windows loader. Easy peasy.
Now have an easy way to change order,default or timeout without messing with editing text files and such.
Win 7 Default
Mint Maya (Cinnamon)
Now just an up or down arrow away from the alternates. Since still have more customizing and configuring Mint before she is ready for Main default.