Assuming you are trying to install OS from cd / dvd - are you sure the PC is booting from the cd / dvd drive.
Most Windows installations flash up the message "press any key to boot from cd"
You should then be presented with an installation screen, select install and follow steps. When you get to the option to format select format as NTFS - if windows and continue.
If no installation screen - check BIOS settings to boot from cd / dvd drive.
You should hear the cd / dvd spinning up through out this process. If it appears to stall it could be as simple as a dirty disc.
Try cleaning it also try making a copy on a separate PC. The installation process can cope with you swapping cds half way through if it has stalled.