I have a PC with Windows 7 on one disk A. Two other disks B and C are software (Windows 7 disk management) RAID1 mirrored. I want to reinstall Windows 7 on the first disk A. Will the new Windows 7 installation recognize the RAID1 set?
Yes. The Windows fault-tolerant disk driver marks RAID volumes such that they will be automatically detected.
If you want to see it for yourself non-destructively just boot the Windows 7 setup DVD, open a command-prompt (Shift-F10), run