Here is couple of quick links that could help.
Are you using the Lenovo disk to install?
Or are you past that? If past that try F8 and boot to VGA mode and see if you get in.
If not try F8 boot logging and see where it stops.
I think the VGA is going to be the one. Usually right about the welcome screen is where windows makes the switch from VGA to your video drivers and is possibly the cause.http://support.microsoft.com/kb/294427http://support.microsoft.com/default.aspx?scid=kb;en-us;308041