I installed Linux Mint 14 alongside Win7 using this tutorial. When I choose Mint in the boot menu, it doesn't boot into Linux. Instead, I get a GRUB4DOS command line. It says something like this:

GRUB4DOS 0.4.5b 2011-11-27, Mem: 630K/3177M/766M, End: 35560D

[ Minimal BASH-like line editing is supported. For the first word, TAB lists possible command completions. Anywhere else TAB lists the possible completions of a device/filename. ]

How do I fix this while leaving windows bootloader as default ?

If you download Rescatux this will fix your Boot Menu. You should find it to be a straightforward process, but please tell us if you need help with it.