Windows failed to start...PLEASE help!

[tracebird]

When I start up my computer, a black screen pops up saying
"Windows failed to start. A recent hardware or software change might be the cause. To fix the problem:
....
I don't have the disk, though. What do I do!?!? Please help!

 

[gregrocker]

Work through these steps for Troubleshooting Windows 7 Failure to Boot.