Hi Queen_of_Aces,
Welcome to Microsoft Answers Forums.
There are several reasons for this error to occur like any hardware device causing the error or any third party program or service and any errors on the hard drive.
Make sure that there are no external devices connected to the computer except mouse and keyboard.
As the computer is able to boot to safe mode there might be some third party program or service causing the error in the normal mode.
To help troubleshoot error messages and other issues, you can start Windows Vista by using a minimal set of drivers and startup programs. This kind of startup is known as a "clean boot." A clean boot helps eliminate software conflicts.
Perform clean boot and check if you have the issue.
1. Click Start, type msconfig in the Start Search box, and then press ENTER.
User Account Control permission
If you are prompted for an administrator password or for a confirmation, type the password, or click Continue.
2. On the General tab, click Selective Startup.
3. Under Selective Startup, click to clear the Load Startup Items check box.
4. Click the Services tab, click to select the Hide All Microsoft Services check box, and then click Disable All.
5. Click OK.
6. When you are prompted, click Restart.
7. After the computer starts, check whether the problem is resolved.
Reset the computer to start as usual
After you have finished troubleshooting, follow these steps to reset the computer to start as usual:
Click Start, type msconfig.exe in the Start Search box, and then press ENTER.
If you are prompted for an administrator password or for confirmation, type your password, or click Continue.
On the General tab, click the Normal Startup option, and then click OK.
When you are prompted to restart the computer, click Restart.
If the issue is resolved check which third party is causing the problem, referring the link given below:
http://support.microsoft.com/kb/929135
If the above step do not fix the issue please try a startup repair of Windows vista for more information refer the below link.
Startup Repair is a Windows Vista recovery tool that can fix certain problems, such as missing or damaged system files, that might prevent Windows from starting correctly. When you run Startup Repair, it scans your computer for the problem and then tries to fix it so your computer can start correctly.
Make system repairs from the Windows Recovery Environment
http://windowshelp.microsoft.com/Windows/en-US/Help/95b4c03a-ac42-49a4-a90d-8f3736a995271033.mspx
How to fix BlueScreen (STOP) errors that cause Windows Vista to shut down or restart unexpectedly
http://support.microsoft.com/default.aspx/kb/958233
Hope this information is helpful.
Let me know if this worked.
All the best!
Thanks and Regards:
Halima S - Microsoft Support.