Something is hanging during startup. Try using the msconfig utility to disable startup items until to find the offending program.
You run msconfig by going to Start Button->Run and typing msconfig and clicking OK
You can start your troubleshooting by selecting Diagnostic Startup on the General tab and then clicking Apply and then OK. Restart your computer, logon and see how long it takes. "If speed is good, then you can run msconfig again, choose Normal Startup and then go to the Startup tab and disable one application at a time, restarting the computer between each, until you find the program that is causing the problem.
Once identified as the offending program, you can try uninstalling it, and reloading it.
If that doesn't fix your problem, check back here and let us know.