Bad Request in apache? Not able to start server?

After installing apache in windows, you may see problems like

Invalid request or Bad request..

This may be because of another program which already using port 80.
you can debug this kind of problems using a command which list
all ports currently in use and program names too

use this command to see which program is using which port
C:\>netstat -a -b -n -o

get PID from above program, and go to task manager to get program / application
name.

In my case svchost is using :http port by default. its may be virus. i terminated it

and you can also see hosts file in
C:\WINDOWS\system32\drivers\etc for any errors.


or if some know program is using 80 port (like tomcat, weblogic...etc) then you
can configure other port like 8888 in httpd.conf ( apache_home/conf)