Well,
I have managed to add some drivers on the image by creating a folder "Drivers" under the root of the primary disk and there copy the driver folders.
On some workstations, this worked ok (As far as I can see from Device Manager) but on an older machine, the audio drivers (AC97 something) are not installed. This probably happens because these drivers are unsigned (I figured it out when trying to manual install the driver on the target machine).
The unattend.xml that I use is the following:
<?xml version="1.0" encoding="utf-8"?>
<unattend xmlns="urn:schemas-microsoft-com:unattend">
<settings pass="oobeSystem">
<component name="Microsoft-Windows-Shell-Setup" processorArchitecture="x86" publicKeyToken="31bf3856ad364e35" language="neutral" versionScope="nonSxS" xmlns:wcm="http://schemas.microsoft.com/WMIConfig/2002/State" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<OOBE>
<HideEULAPage>true</HideEULAPage>
<NetworkLocation>Work</NetworkLocation>
<ProtectYourPC>1</ProtectYourPC>
<SkipMachineOOBE>true</SkipMachineOOBE>
<SkipUserOOBE>true</SkipUserOOBE>
</OOBE>
<Display>
<ColorDepth>32</ColorDepth>
<DPI>96</DPI>
<HorizontalResolution>1024</HorizontalResolution>
<RefreshRate>60</RefreshRate>
<VerticalResolution>768</VerticalResolution>
</Display>
<RegisteredOwner>Template</RegisteredOwner>
<RegisteredOrganization>Company</RegisteredOrganization>
<TimeZone>GTB Standard Time</TimeZone>
</component>
<component name="Microsoft-Windows-International-Core" processorArchitecture="x86" publicKeyToken="31bf3856ad364e35" language="neutral" versionScope="nonSxS" xmlns:wcm="http://schemas.microsoft.com/WMIConfig/2002/State" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<SystemLocale>en-US</SystemLocale>
<UserLocale>en-US</UserLocale>
</component>
</settings>
<settings pass="specialize">
<component name="Microsoft-Windows-Shell-Setup" processorArchitecture="x86" publicKeyToken="31bf3856ad364e35" language="neutral" versionScope="nonSxS" xmlns:wcm="http://schemas.microsoft.com/WMIConfig/2002/State" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<ProductKey>XXXXX-XXXXX-XXXXX</ProductKey>
<ComputerName>*</ComputerName>
</component>
<component name="Microsoft-Windows-UnattendedJoin" processorArchitecture="x86" publicKeyToken="31bf3856ad364e35" language="neutral" versionScope="nonSxS" xmlns:wcm="http://schemas.microsoft.com/WMIConfig/2002/State" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<Identification>
<JoinWorkgroup>Domain</JoinWorkgroup>
</Identification>
</component>
</settings>
<settings pass="generalize">
<component name="Microsoft-Windows-PnpSysprep" processorArchitecture="x86" publicKeyToken="31bf3856ad364e35" language="neutral" versionScope="nonSxS" xmlns:wcm="http://schemas.microsoft.com/WMIConfig/2002/State" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<PersistAllDeviceInstalls>true</PersistAllDeviceInstalls>
</component>
<component name="Microsoft-Windows-Security-Licensing-SLC" processorArchitecture="x86" publicKeyToken="31bf3856ad364e35" language="neutral" versionScope="nonSxS" xmlns:wcm="http://schemas.microsoft.com/WMIConfig/2002/State" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<SkipRearm>1</SkipRearm>
</component>
</settings>
<settings pass="offlineServicing">
<component name="Microsoft-Windows-PnpCustomizationsNonWinPE" processorArchitecture="x86" publicKeyToken="31bf3856ad364e35" language="neutral" versionScope="nonSxS" xmlns:wcm="http://schemas.microsoft.com/WMIConfig/2002/State" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<DriverPaths>
<PathAndCredentials wcm:action="add" wcm:keyValue="1">
<Path>c:\drivers</Path>
</PathAndCredentials>
</DriverPaths>
</component>
</settings>
<cpi:offlineImage cpi:source="wim:c:/vista/x86/image.wim#Windows Vista ULTIMATE" xmlns:cpi="urn:schemas-microsoft-com:cpi"/>
</unattend>
I have found a way to override this problem for unsigned drivers but only for the sysprep version of windows XP.
Any Ideas?