On some XP based PCs with Office 2003 installed,Internet Explorer may close
immediately after it has been lunched.You get no error message.Responsible
for this is the Owcsclt.dll file which adds the Discuss toolbar to the
Internet Explorer.The Owcsclt.dll will be installed as a COM component by an
Office 2003 Installation.To resolve this problem the Discuss toolbar needs
to be removed by deleting the responsible key in the registry or unregister
the responsible dll file.To delete the key in the registry navigate to :

- HKEY_CLASSES_ROOT\CLSID\{BDEADE7F-C265-11D0-BCED-00A0C90AB50F}

delete here the in the left pane the key:

{BDEADE7F-C265-11D0-BCED-00A0C90AB50F}


or you can unregister the dll by bringing up a command prompt and typing :

regsvr32/u Owsclt.dll


Note:
I have XP and Office 2003 installed on my laptop at work and had it on my PC
at home and the mentioned symptoms did not occur with me.