Date: 06/21/07 (Apache)    Keywords: apache

I guess lots of people (including me) are having problems getting Apache to work on Vista. I don't know if anyone's already posted this solution, but I pieced it together from a few different sites that each offered their own little tidbit. I hope this helps someone:

1) if you have already been trying to make this work, make sure you completely remove and detele all evidence of apache 2.2.4 from your computer: program files, registry, etc. if you haven't had a failed install attempt and you're starting fresh, go on to step 2.
2) turn off User Access Control
2) run cmd.exe as an administrator. you can do this by right-clicking on the link in the start menu program list.
3) from the command line, go to the directory your apache msi file is in. enter: "msiexec /i .msi" (without the quotes obviously)
5) let the program run, check off everything as you see fit. when the program has finished running, it will most likely display an error popup. close this.
6) back on the command line (still running as administrator), go to \bin and enter: "httpd -k install"
7) now apache should show up as a service. but you're not done yet! go to the apache monitor/control thingy in your start menu. right-click it and go to properties->compatibility. set the compatibility mode to winxp sp2.
8) that's it! you may want to start your apache control, but it will run now without that.

Source: http://community.livejournal.com/apache/37811.html