Unplug all USB things and try again.
I just upgraded to Windows 7 on my Toshiba Satellite Special Edition laptop that came with Vista 64bit and the other night i downloaded iTunes 10 and told me to restart my machine so I clicked ok and then my laptop shut off and when it came back on the Toshiba screen came up as usual but seemed to stay on longer than normal then it goes to a black screen with a underscore that blinks for a few moments then becomes solid. Ive tried to use the "F" keys to get different boot options because i have the windows 7 ISO disc and a ubuntu disc that I could use but whatever i try my laptop wont process it just does the same thing over and over again and bever proceeds to the actually boot up windows. what could be going wrong and how can i fix this? i'm seriously thinking about staying with linux...since vista and W7 have been screwing up terribly the past 2 months.