If your PC isn't working correctly, it could be that that is causing Windows to report corruption on the disc. I'm not saying the disc isn't corrupted, but whatever caused it to be corrupted could be causing it to report corruption (that made sense when I wrote it
Also, if you try to fix it, it could cause more corruption.
If you have any data you want to keep, I would make sure you have it backed up, and then probably would do what nekro suggested and re-install Windows. I suggest thaat because you had 32-bit Windows working without issue and have not made any hardware changes in moving to 64-bit. Is that correct?
It doesn't take long to install Windows, and I don't think I would trust anything on my PC without a re-install. If there are corrupted files reported by Windows, you can almost guarantee there are othher corrupted files that Windows does not check (except through CHKDSK).
Go for a reinstall instead of a repair would be my advice. As they say in Aliens, "It's the only way to be sure".