[ubuntu] problem with installing ubuntu in dell inspiron with windows 8

I recently bought a new laptop dell inspiron pre-installed with windows 8. The first thing I did was installing ubuntu and made it to boot with ubuntu by default. Now the problem is whenever I run windows 8, ubuntu never loads after that. Then I reinstalled it and again by default it boots to ubuntu. Again when i ran windows 8 today. Ubuntu stopped.

I think that windows 8 is altering the grub boot loader. Please tell me the solution for it.
I really really need ubuntu on it.