If you're not going to reinstall Windows, you should be able to first fix the MBR with your windows disk (select repair) and then run fixmbr.
Anyway, once you fix the mbr so that it uses NTLDR again, in Windows just right click on My Computer and select "Manage". Then go into "Storage" --> "Disk Management(Local)". From there, you should be able to select the other partition and delete it/reformat it. I'm not sure if you can "grow" the system from there or not. If not, I would download GParted LiveCD
and use that to grow the C: partition.