[Windows Mobile] hilaireg:
An OEM package is essentially a kitchen package. The term OEM came about partly because the ROM extraction tools - essentially, the tools extract the content of an OEM .NBH/.NB file. An OEM package usually consists of files, files as modules, <guid>.dsm, <guid>.rgu, shortcuts, *.provxml, *.txt, and *.dat.

When chefs refer to OEM packages, they are generally speaking about the folders that appear in .\OEM, .\SYS, and the .\PACKAGES (or .\EXT) folder. Here is some background for Ervius Package Builder (PkgBuildOS) & Ervius Visual Kitchen (EVK).

PkgToolsBuildOS

In the older PkgBuildOS kitchen, the OEM package had a relatively flat structure. Most OEM packages were prefixed with 'PACKAGE_' - chefs would see these folders in .\OEM and .\SYS. It was also preferable to move such folders into a '.\PACKAGES' folder structure making it easier to choose which packages to include during the ROM compilation. Ideally, chefs would only keep essential (critical) packages in the .\OEM and .\SYS. The structure of the OEM package would look similar to the following:

[B][COLOR="Blue"]<PACKAGE_oem_packagename>[/COLOR][/B]
[INDENT]<guid1>.rgu [COLOR="Purple"][I](<guid1>.rgu + <guid2>.rgu)[/I][/COLOR]
<guid1>.dsm
[COLOR="Purple"]<guid2>.dsm [I](removed)[/I][/COLOR]
files
*.provxml
shortcuts
*.txt
*.dat
option.xml

[B][COLOR="Blue"]<modulefoldername>.[[COLOR="Green"]ext[/COLOR]][/COLOR][/B] ([COLOR="green"][B]ext [/B][/COLOR]= dll, cpl, ocx, etc.)

[INDENT]imageinfo.bin
imageinfo.txt
S0001
S0002
S0003
...
[/INDENT]
[/INDENT]

Visual Kitchen

When Ervius created the Visual Kitchen, he also created a tool to convert old PkgBuildOS OEM packages into the new kitchen format. During the conversion process, the tool would read the .DSM filename information and rename the folder accordingly - sometimes a folder would be prefixed with 'PACKAGE_' and in other cases not; it depended on the internal .DSM name. The new format of the package was such that it divided the language-specific files into a sub-folder within the EVK OEM package.

Additionally, the tool would copy the OEM packages to the .\EXT folder as once again, it is preferable to have OEM packages in the '.\EXT' folder structure as it makes it easier to choose which packages to include during the ROM compilation. Ideally, chefs would only keep essential (critical) packages in the .\OEM and .\SYS. The structure of the OEM package would look similar to the following:

[B][COLOR="blue"]<oem_packagename>[/COLOR][/B][INDENT]<guid>.rgu
<guid>.dsm
app.reg
app.dat
_skip

[B][COLOR="blue"]Files[/COLOR][/B][INDENT]*.provxml
shortcuts
*.txt
*.dat

[B][COLOR="Blue"]<modulefoldername>.[[COLOR="Green"]ext[/COLOR]][/COLOR][/B] ([B][COLOR="green"]ext [/COLOR][/B]= dll, cpl, ocx, etc.)[INDENT]imageinfo.bin
imageinfo.txt
S0001
S0002
S0003
...
[/INDENT]
[/INDENT]

[B][COLOR="red"]<LANG> [/COLOR] ([COLOR="red"][B]LANG[/B][/COLOR] = 0409, 040C, etc.)[/B][INDENT]<guid2>.rgu
<guid2>.dsm
app.reg
app.dat
_skip

[B][COLOR="blue"]Files[/COLOR][/B][INDENT]*.provxml
shortcuts
*.txt
*.dat

[B][COLOR="Blue"]<modulefoldername>.[[COLOR="Green"]ext[/COLOR]][/COLOR][/B] ([B][COLOR="green"]ext [/COLOR][/B]= dll, cpl, ocx, etc.)[INDENT]imageinfo.bin
imageinfo.txt
S0001
S0002
S0003
...
[/INDENT]
[/INDENT]
[/INDENT]
[/INDENT]

The tutorials I put together for the Visual Kitchen (EVK) and Package Builder (PkgToolsBuildOS) provide some additional details about the folder structure of the kitchen so I won't get into more details about it here.

HTH,