What worked for me was to use the IPv4 version of 'localhost' in my hosts file. The 'hosts' file is usually located in the C:\Windows\System32\drivers\etc
directory on most systems. Editing the 'hosts' file was a pain in the neck. You can't simply right click or double-click to open the file. You first have to fire up Notepad or your favorite editor using "Run As Administrator" (right-click) and then hunt for the file using the "File -> Open" dialog. Windows prevents editing that file normally (a good thing) but then get in the way of actually editing it (a bad thing).
Anyway, under Windows 7, the following two lines are commented out:
# 127.0.0.1 localhost
# ::1 localhost
Uncomment the first line but leave the second commented:
127.0.0.1 localhost
# ::1 localhost
Save the file. Try loading pages in Apache again. Should be back to normal speed.
Source :
http://cubicspot.blogspot.fr/2010/07/fixing-slow-apache-on-localhost-under.html