PC won't boot... tcpip.sys is corrupt..Need help?

Use a system repair disk or a Windows installation disk and boot to the recovery console and run system restore. Restore your system to a point prior to you having this issue. Once system restore completes, reboot your computer and your problem will be fixed. If you can't do that try booting into Safe Mode by pressing F8 and do a system restore. If you know of someone else who has a computer with Windows Vista, go into the Windows Backup Utility and create a system repair disk from there and it will work on your computer as well.