First, Welcome to SitePoint's Apache forum.
As Dan said, there are MANY things which could have caused the problem. Failure to start is generally a sign that your httpd.conf has some bad syntax in it but a power failure is not a likely source of an error like that.
From the lack of any further information, I'd think the problem is that, when you installed Apache, you didn't PREVENT IIS from starting with WinDoze. Check Start | Run and services.msc to see whether IIS has confiscated port 80. If not, then you probably have corrupt files (and a damaged HD) due to the power surges when the power came back on.
Sorry for that news.