You may come across a common issue found in Magento after installation.
That you are unable to login from admin even you are giving the correct credentials like
username:admin
password:123123
Solution:
1. Mostly solution to this problem is simple that you should open up your host file placed at
C:\WINDOWS\system32\drivers\etc
and add following lines in it
127.0.0.1 magento.localhost.com
then to flush you dns open Windows->Run and type this command to flush your DNS
ipconfig /flushdns
or you can simply reboot your system
2. Then you have to access your site as
http://localhost.com/magento
missing the ".com" after localhost will result in the previous error as Magento needs a domain name with dot('.') in it.
The environment on which i have tested this solution is
Windows XP,Apache 2.2 Zend and Magento with Zend server
