SCCM is my weapon of choice but I have found that sometimes even if a machine is placed in the 64bit deployment collection with the 64bit deployment task sequnce advertsied; it will still throw out the 32bit PE.
This is if a collection has multiple advertisments it will churn out the latest image to be advertised. To get around this I found a great article on "Network Steve" that I have included below:
I had the exact same problem;
I wanted to be able to boot x86 or x64 Unknown Computers and image them. I have figured a very simple and erffective work around to this problem of the last advertised task winning...
I edited the query in the Unknown Computers collection to add: and Name LIKE "%x86%"
here's the complete query for the "Unknown Computers" collection
select SMS_R_UNKNOWNSYSTEM.ResourceID,SMS_R_UNKNOWNSYSTEM.ResourceType,SMS_R_UNKNOWNSYSTEM.Name,SMS_R_UNKNOWNSYSTEM.Name,SMS_R_UNKNOWNSYSTEM.Name from SMS_R_UnknownSystem where Decommissioned = "0" and Name LIKE "%x86%"
Then I created a new collection called "Unknown Computers x64" and used the following query:
select SMS_R_UNKNOWNSYSTEM.ResourceID,SMS_R_UNKNOWNSYSTEM.ResourceType,SMS_R_UNKNOWNSYSTEM.Name,SMS_R_UNKNOWNSYSTEM.Name,SMS_R_UNKNOWNSYSTEM.Name from SMS_R_UnknownSystem where Decommissioned = "0" and Name LIKE "%x64%"
Next, Advertise your x86 Task Sequences to the Unknown Computers query and your x64 Task Sequences to the Unknown Computers x64 query.
Now, as long as the computer is not in the SCCM database, when you PXE boot it will get the correct image.
Good LuckDoug
http://www.networksteve.com/enterprise/topic.php/Boot_Image_pulling_wrong_Windows_PE_interface/?TopicId=25850&Posts=4
