fix_hdc should work: http://www.911cd.net/forums/index.php?showtopic=20464 I think it's in ubcd4win, which might be easier than building your own bartpe and maybe integrating mass storage drivers: http://www.ubcd4win.com/
Eh? Raid 5 copes with the loss of a single disk, and the data remains available for read/write, just at increased risk. If the raid card can't rebuild the array while it's up, it's not a very good one.
What are the IP addresses and netmasks? If B is doing NAT but C has a routable address then you might be able to connect to it, but if A is doing NAT then you're probably out of luck...