i get a white screen when trying to reinstall snow leopard

I am trying to install snow leopard over os x mavericks when i put the disc in it tells me to restart the computer, when it boots up the screen goes white and stays that way the only way I can get out of this is to push and hold the power button and when it reboots hold the eject button on the keyboard to eject the disc or it goes back to white screen, how can I get the reinstall to work ? the system is a iMac 27" mid 2010 3.2 ghz 4gb ram 1 tb hd I bought this used and thought I could get a clean install by updating to os x mavericks when it didn't I got the snow leopard disc to try and put the original software back on