As Greg said I would not want to run an OS with that level of corruption but to me it sounds like you only want to get rid of the option to select which OS to boot into.
Quote:
Now i can regularly use the pc if before booting that screen if i press up and down keys alternatively until i can choose to continue Windows 7 installation or start windows. In that way the pc works fine.
If I'm reading right you have two choices on bootup, Windows 7 Installation and Windows 7, and if you select Windows 7 your computer boots and run fine.
If that is true you can run MSConfig, click the boot tab and delete the Windows 7 Installation from the list or you can just make Windows 7 the default. And check the box, Make all boot settings permanent.
Backing up your data and doing a clean reinstall would be much better though.