You can identify if the computer is Laptop or Desktop based on its chassis Types.

Below are listed the Chassis types available to create SCCM collection or reports.

For Laptops Chassis Types : 8 , 9, 10, 11, 12, 14, 18, 21

For Desktop Chassis Type : 3, 4, 5, 6, 7, 15, 16

For server Chassis Type: 23

Below is the collection to list all the computers which are laptops which fall in above Chassis type. All these values are from SQL table called SMS_G_System_SYSTEM_ENCLOSURE .If you are looking to create SCCM report,you can create using Views(v_GS_SYSTEM_ENCLOSURE).

You can also replace the values with Desktop computers or servers also you can use joins to club these with AD groups for deploying the applications based on this.

select SMS_R_System.ResourceId, SMS_R_System.ResourceType, SMS_R_System.Name, SMS_R_System.SMSUniqueIdentifier, SMS_R_System.ResourceDomainORWorkgroup, SMS_R_System.Client from SMS_R_System inner join SMS_G_System_SYSTEM_ENCLOSURE on SMS_G_System_SYSTEM_ENCLOSURE.ResourceID = SMS_R_System.ResourceId where SMS_G_System_SYSTEM_ENCLOSURE.ChassisTypes in ( “8”, “9”, “10”, “11”, “12”, “14”, “18”, “21” )

Here are some sample reports/queries available which you can make use of it

http://myitforum.com/cs2/blogs/snorman/archive/2007/09/18/count-of-chassis-types-by-collection.aspx

http://wmug.co.uk/wmug/b/eskonr/archive/2010/11/16/sccm_2d00_collection_2d00_to_2d00_list_2d00_all_2d00_the_2d00_laptop_2d00_computers