If you use "fdisk /mbr" you will not lose partitions, only the MBR is rewritten. However, it is always best to backup anything important before doing anything on such a base level. That said, I have never had any problems with "fdisk /mbr". Hope this works for you. After you get things to work, make sure you run chkdsk on all of your partitions. There are bound to be some lost clusters somewhere after all this trouble.