PROBLEM WITH MBR

I have 4 primary partitions-C(WIN,FAT32),one extended and the other 2 are free space.(Once I had Linux on one of them).I want to format them under FAT32(I use Partition Magic)but whenever I try to do this i get an error message:”Unable to write to the boot sector”.I get such messages with all kinds of programmes that write to the MBR and I also can’t reinstall WIN.(Can’t install LINUX too).
Thanks in advance.