Well the default installation for apache is
"\Program Files\Apache Software Foundation\Apache2.2\"
Now we need to start apache.
You can either choose to run apache as service or from command line.
Go to start and select run, then type in cmd and hit enter.
then type
c:
cd "\Program Files\Apache Software Foundation\Apache2.2\bin"
httpd -k install
there are more options but this is the default.
For the command line
Go to start and select run, then type in cmd and hit enter.
at the prompt type in
apache
or
c:
cd "\Program Files\Apache Software Foundation\Apache2.2\bin"
httpd
if there is a problem you can go to
\Program Files\Apache Software Foundation\Apache2.2\logs
and look through the error.log to see whats wrong.
Now you want to leave that command line window open and you should be able to type in http://localhost and see your site.
Now if you are still have problems and you know that apache is running successfully, you might perhaps want to check your windows firewall if its running or any other firewall software you may have.
This is just a quick help, there is more information available at
http://httpd.apache.org/docs/2.2/platform/windows.html
Last time I checked there is a folder inside of
\Program Files\Apache Software Foundation\Apache2.2\
called htdocs and you should be able to find your default pages there and put any additional pages you want there to.
This again is just the default setup, You didn't give enough information to tell you exactly what to do for your setup, like where you installed apache, whether you know for sure port 80 is open, etc, etc.
I hope this helps.
Good Luck