I recently updated my work laptop to 64-Bit Windows 7 so that I could up my RAM, and found that after installing CF IIS 7.0 threw 0x800700c1 errors. Luckily, after some googling, I found the answer.
The error message I was getting was a 500 server error, specifically "0x800700c1", which helped lead me to this forum post explains that CF ISAPI is 32 bit only, and goes on to describe how to solve the problem. In short, you need to open your Command window (with Admin permissions), and paste in the following code:
Worked like a charm!