Increase PC Performance: Repair Startup Issues
Yahoo! Tech has a detailed post on how to fix startup issues.
I will go through some of them in detail.
- Try to get Windows started by using the tools on the Windows Advanced Options menu (see Figure 1). Remove any media from optical drives and floppy drives and restart your computer. Just before Windows starts, press the F8 key to bring up the Windows Advanced Options menu. There's only a brief window of time when you can press the F8 key to access Windows Advanced Options. If you're not sure when to press the key, repeatedly press the key throughout the boot process until you see the menu.
- If you have just installed a new graphics card driver, use the arrow keys on your keyboard to select Enable VGA Mode from the Windows Advanced Options menu. This forces Windows to start with a resolution of 640×480, bypassing any conflict with your monitor in the current driver settings. If Windows starts, check your monitor's manual and set the graphics driver at a resolution supported by your monitor.
- If you've just installed new hardware or software and rebooted your computer, try selecting Last Known Good Configuration (Your Most Recent Settings That Worked). This loads the basic Windows settings that were used the last time Windows started successfully.
For a complete how to on fixing startup issues check the following link.