IIS and Apache/Wamp are both web server and both use port 80, so you have to disable IIS in order for Wamp to work
Disable IIS in Vista:
Uninstall Programs, Turn Widows Features On or Off, uncheck Internet Information Services
Disable IIS in XP:
Add/Remove Programs, Add/Remove Windows Components, uncheck Internet Information Services (IIS)
Restart computer, then restart Wamp
Have fun,
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