Leopard Upgrade White Screen Of Death

[macsmack]

I just upgraded my imac from Tiger to Leopard OS; was super excited and wanted to install Windows XP as well but after the upgrade had finished, I completed the registration, and then proceeded in opening Boot Camp to install Windows XP. I took out the Leopard disc, selected a partition size, and put in my Windows XP cd. But during this process, Leopard needed to restart, so I did, as it restarted the Windows XP cd was still in and started to run to the whole scanning process; I got as far as pressing "Do you want to install Win XP" but realized it was asking me to "format" but I did not go thru with it so I canceled it. So, I turned off the imac and restarted, managed to get out the Windows XP cd and had just a plain white screen. Leopard did not load, nothing. I restarted, waited for a while, and turned it back again still the white screen comes out. Any ideas, just to get it to load the Leopard OS again???