• Start > Run > secpol.msc
• Expand software restriction policies.
• Right click Additional Rules > New Path Rule
• Path:C:\Program Files\Outlook Express\msimn.exe.
• Security Level: Disallowed.
• Click OK

OR

• Start > Run > secpol.msc
• Right click Software Restriction Policies > Create new policy
• Expand software restriction policies
• Right click Additional rules > New Path Rule
• Path: C:\Program Files\Outlook Express\msimn.exe
• Security Level: Disallowed
• Click OK
  

Please note this is for experienced xp pro users.