apache does not work, port 80 is used by...

Look in the Listening Ports section of the Network tab in Resource Monitor. If something is using 80, then it will show up there.

hey .. look what i did when same problem faced me :
open httpd.conf in notepade
replace the two lines have:
127.0.0.1:80
with:
127.0.0.1:81
Save and restart Apache
everything work nice again.
greets

Did WAMP install apache as a service ? Check in services and see if it is started ... if not, start it.