Unplug all your external and internal devices except the graphics card and see if it boots into Windows
If not, remove the lan, wlan connection and boot into Safe Mode (F8)
Go to Device Manager, Display adapter and opt to update the driver
, browse for the driver in my computer, let me pick and choose standard vga graphics adapter. Reboot the system
Once at the desktop, go to Control Panel Windows Update and configure Windows Update to download updates but let you choose what to install. Plug in the LAN/WLAN/ connect to the internet (or via modem)
Scan for driver updates on Windows Update and install everything but the graphics driver.
Once everything installs, reboot and continue running Windows Update until it says your system is up to date
Run the Windows 7 Upgrade advisor to see if your graphics card is supported.
a. If not, get a new or used graphics card or just use it as is.
b. If it is supported, install the driver from Windows Update