OK the final resolutions to this problem: Thanks for all the help everyone!!
Here from Symantec:
Dell Optiplex 745 computers cannot start in normal mode after installing Symantec AntiVirus 10.1
Symptom
Dell Optiplex 745 computers cannot start in normal mode after installing Symantec AntiVirus 10.1
You install Symantec AntiVirus 10.1 or Symantec Client Security 3.1 to a Dell Optiplex 745 computer with a dual core chip. When you restart the computer, Windows cannot start in normal mode.
Resolution
Symantec is investigating this problem to determine a solution. This document will be updated when new information or a solution is available.
To work around the problem, create the UseVolumeInfoList registry value and set the value to 0. Then, restart the computer.
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WARNING: In the next steps you will edit the Windows registry. Back up the registry before you make any changes to it, because incorrect changes to the registry can result in permanent data loss or corrupted files. Modify only the registry keys that are specified.
For instructions, see How to back up the Windows registry.
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To create the UseVolumeInfoList registry value
On the Windows taskbar, click Start > Run.
In the Open box, type the following text:
regedit
Click OK.
In the Windows Registry Editor, in the left pane, go to the following key:
HKEY_LOCAL_MACHINE\SOFTWARE\Intel\LANDesk\VirusProtect6\CurrentVersion\Storages\Filesystem\RealTimeScan
Right-click the RealTimeScan key, and then click New > DWORD Value.
Type UseVolumeInfoList for the value's name, and then press Enter.
In the right pane, double click the UseVolumeInfoList value.
In the Value data box, type 0
Click OK.
Restart the computer.
To ensure the best performance, Symantec recommends that you update the Symevent drivers as well. For instructions, read the document Updating the Symevent files.
http://entkb.symantec.com/security/output/n1998092408260848.html