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#11
Two things I would look at here. First, I would disable Asus Express Gate in the BIOS, if possible. I'm not sure how that works, but I would get it out of the way for testing purposes. Could be that the BIOS needs flashing.
Second, it may be that your C drive's MBR is messed up. I would use a boot disk to view the drive independently. Hiren's BootCD has a superb free tool, TestDisk, that will find the partitions, ascertain that the disk's partition table is sound, and make corrections to it if necessary.