There are OEMLogo.bmp (96x96) for OEMLOGO and OEMInfo.ini for OEM information used to add under windows XP
Copy both files under X:\Windows\System32\
But In Windows Vista, has been changed the method to add OEM information in System properties.
All things are added through Windows registry instead using OEMinfo.ini file.
Here is some code of registry to add OEM info in Windwos Vista

CODE
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\OEMInformation]
@=""
"Manufacturer"="Hewlett-Packard"
"Model"="Compaq Presario SR1610IL"
"Logo"="C:\\Windows\\system32\\oemlogo.bmp"
"SupportPhone"="1-600-114772 (Toll free), 0124-2346992 (Toll Number)"
"SupportURL"="http://www.hp.com/in/support"
"SupportHours"="9 AM to 9 PM (Mon-Sat)"
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\OEMInformation]
@=""
"Manufacturer"="Hewlett-Packard"
"Model"="Compaq Presario SR1610IL"
"Logo"="C:\\Windows\\system32\\oemlogo.bmp"
"SupportPhone"="1-600-114772 (Toll free), 0124-2346992 (Toll Number)"
"SupportURL"="http://www.hp.com/in/support"
"SupportHours"="9 AM to 9 PM (Mon-Sat)"
Here We can see that there is no need to put OEMlogo.bmp file in X:\Windows\System32.
We can locate the file in the any location by setting Logo value