Bootloader problem Grub.

Hello,

I have some questions about my Mandriva Linux. My father died last year and so I got automatically forced to use Linux (master computer). I have become a little bit known with it, had to reset the root password via command lines etc. But I have some problems I can't solve on my own.
In this topic I will ask my first problem:

The Grub bootloader doesn't open Windows when clicking on it. Sometimes it just reboots and you get the Grub bootloader again, sometimes when I messed with some things it says something like this:

I have tried everything I thought that could help, placing the boatloader in another disk (which made me use the rescue cd, because nothing would startup anymore :D), placed the bootloader back, using the other bootloader Lilo which didn't work well and so on.

I have changed the link in the bootloader from sdb1 (Windows was given that command automatically at installation) to sdc1 because at the diskpartition the windows C stands at sdc1. But nothing changes. Images:

Who can help me. I can reach the windows files via /mnt but not just how it has to work. Deleting windows or Linux is no option, there are too many important files on both.

Bij voorbaat dank as we say here...