UPDATE:
In case it helps anyone else, I finally found out what was using port 80 for me and thus blocking Wamp. It was not easy to track down, since I had already shut down all that was suggested (see my earlier post in this topic).
Here's how to find out what's using port 80 in Windows XP:
1) Go to START-->Run and type cmd to bring up a Command prompt
2) In the Command Prompt window. type netstat -aon.
This will bring up a list of the ports and what's Listening on them. Look for the one ending in :80 (yes there's a colon between the IP address and the port, so it may look something like 127.0.0.0:80)
3)To the right of the IP address ending in :80, you should see that the port is "listening", and to the right of the listening state, there's a PID (Process Identifier) number. Make a note of that number.
>>> Another method for finding out the port number is to download the fport utility:
[
www.foundstone.com]
Unzip it, place it in the root of c:\ , then in the command prompt window type in c:\fport. It will list out all the ports and what processes are using them. Much faster to do.<<<
4) Open up the Windows Task Manager. In order to see the PID numbers of the various processes, so you can identify which process is using Port 80, click on the Processes tab, then choose View-->Select Columns from the menu. Check the box next to PID (Process Identifier). You'll now be able to see which process matches up with the PID number you noted earlier. If you used fport, you'll already know which program it is.
5) Once you've identified the process using port 80 you'll know which program you need to shut down. It saves some guessing as to which process is using port 80, and may mean that you won't have to shut down your antivirus, etc. in order to clear that port.
Pat